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THE

JOHN MURRAY EXPEDITION T933"34

VOLUME X

\

V

BRITISH MUSEUM NATURAL HISTORY

THE

JOHN MURRAY EXPEDITION

1933-34

SCIENTIFIC REPORTS

VOLUME X 1953-1964 ZOOLOGY

TRUSTEES OF THE BRITISH MUSEUM (NATURAL HISTORY)

LONDON : 1970

© Trustees of the British Museum (Natural History), 1970

Publication No. 686 Standard Book No. 56500686 X

PRINTED IN ENGLAND BY STAPLES PRINTERS LIMITED AT THEIR

KETTERING, NORTHANTS, ESTABLISHMENT

CONTENTS

2

o«t

Page

Xo. 1. The Pelagic Tunic at a. By R. B. Seymour Sewell.

Introduction ............

Larvacea ............

Acopa .............

Doliolida ............

Pvrosomida ............

List of References ...........

Pp. 1-90; 1 pi. [Issued November 27th. 1953.]

1

3

8

45

55

87

Xo. 2. Scaphopoda. By X. H. Ludbrook. 91

List of References . . . . . . . . . . .118

Pp. 91-120; 1 pi.

[Issued January 29th. 1954.]

Xo. 3. Cephalochordata. By J. E. Webb.

Introduction Systematic account List of References .

Pp. 121-128 [Issued January 29th. 1957.]

121

122

128

Xo. 4. The Sessile Tunicata. By P. Kott.

Summary .... Introduction .... Enterogona .... Pleurogona .... List of References .

Xo. 5. Sponges. By M. Burton.

Introduction .

List of species

Hexactinellida

Calcarea

Tetraxonida .

Lithistida

Keratosa

List of References .

129

129

130

144

148

Pp. 129-149.

[Issued May 17th. 1957.]

151

151

176

180

181

216

268

273

Pp. 151-281. [Issued November 24th, 1959.]

No. 6. Report on the Brachiopoda of the John Murray Expedition.

By H. M. Muir-Wood.

Introduction ........... 283

Stations at which Brachiopods were dredged ...... 284

Previous expeditions to the Indian Ocean and records of Brachiopods . 285

Species of Brachiopods previously obtained from the Indian Ocean . . 288

Inarticulata ........... 289

Articulata ............ 290

Conclusions and summary . . . . . . . . .311

List of References ........... 315

Pp. 283-318; 5 pis.

[Issued November 24th, 1959.]

No. 7. Crustacea: Penaeidae, Part II. Series Benthesicymae. By N. M. Tirmizi.

Introduction ........... 319

Station list and distribution map ........ 320

Diagnosis of series Benthesicymae . . . . . . . .321

Key to determination of genera examined ...... 322

Systematic account .......... 322

List of References ........... 382

Pp. 319-383.

[Issued January 29th, I960.]

No. 8. Crustacea: Chirostylidae (Galatheidea). By N. M. Tirmizi. 385

List of References ........... 414

Pp. 385-415. [Published December 30th, 1964.]

PLATES

No. 1. PI. I. fig. 1. Jletcalfina hexagona (Quoy ancl Gaimard).

2. Pyrosoma verticiUatum Neumann, forma cylindricum Metcalf and Hopkins.

3. Pyrosoma verticiUatum Neumann, forma hydridum Metcalf and Hopkins.

4. Pyrosoma aherniosum Seeliger.

5. Pyrosoma atlanticum (Peron).

No. 2. PI. I, fig. 1. Dentalium (DentaUum) octangulatum Donovan.

2. DentaUum ( DentaUum ) adenense sp. nov.. holotype.

3. DentaUum (DentaUum) pseud osexagonum Deshayes.

4. DentaUum (Antalis) usitatum Smith.

5. DentaUum ( Tesseracme ) quadrapicale Sowerby.

6. DentaUum ( Lcevidentalium ) leptosceles (?) Watson.

7. DentaUum ( F issidentalium ) perinvolutum sp. nov.. liolotype.

8. DentaUum (Lcevidentalium) curvotracheatum Plate.

9. DentaUum ( Pseudantalis ) rubescens var. tenuifissum Monterosato.

10. DentaUum (Episiphon) sewelli sp. nov.. holotype.

11. DentaUum ( Episiphon ) minutissimum sp. nov.. holotype.

12. Cadulus (Cadulus) cyathoides Jaeckel.

13. Cadulus (Cadulus) campylus Melvill.

14. Cadulus (Polyschides) hexaschistus Boissevain.

15. Entalina mirifica Smith.

16. Entalina incequisculpta sp. nov., holotype.

17. Entalina adenensis sp. nov., holotype.

18. Cadulus ( Gadila ) anguidens Melvill and Standen.

19. Cadulus (Gadila) euloides Melvill and Standen.

20. Cadulus (Gadila) reesi sp. nov.. holotype.

21. Cadulus (Gadila) subcolubridens sp. nov.. holotype.

22. Cadulus (Dischides) dichelus Watson.

23. Cadulus (Dischides) oval is Boissevain.

24. Cadulus (Dischides) prionotus Watson.

No. 6. PI. I. fig. la-d. Dyscolia johannisdavisi (Alcock).

2a-b. Dyscolia wyvillei (Davidson).

3a-c. Dyscolia johannisdavisi (Alcock).

4a-b. Dyscolia johnanisdavisi (Alcock).

II, fig. 1. Dallithyris murrayi gen. et sp. nov.

2a-c. Dallithyris cubensis (Pourtales).

3a-b. Dallithyris cubensis (Pourtales).

4a-c. Dallithyris murrayi gen. et sp. nov.. holotype.

5. Dallithyris murrayi gen. et sp. nov.

6. Dallithyris murrayi gen. et sp. nov.. paratvpe.

7. Dallithyris murrayi gen. et sp. nov.. paratype.

8. Dallithyris murrayi gen. et sp. nov.. holotype.

ITI. fig. 1. Dallithyris murrayi gen. et sp. nov.. holotype.

2a-b. Dallithyris murrayi gen. et sp. nov., paratype.

3a-b. Dallithyris murrayi gen. et sp. nov., paratype.

4a-b. Dallithyris murrayi gen. et sp. nov., paratype.

5. Liothyrella uva (Broderip).

6. Dallithyris cubensis (Pourtales).

7. Gryphus vitreus (Born).

8. Chlidonophora incerta (Davidson), syntype.

IV, fig.

1. Terebratulina retusa (Linne).

2a-b. Eucalathis murrayi (Davidson), syntype.

3. Eucalathis murrayi (Davidson), syntype.

4. Chlidonophora incerta (Davidson), syntype.

5. Chlidonophora chuni (Blochmann), topotype.

6. Chlidonophora chuni (Blochmann).

7a— b. Chlidonophora chuni (Blochmann).

8. Lingula sp.

9. Leptothyris ignota gen. et sp. nov., holotype.

V, fig. la-b. Cryptopora maldivensis sp. nov., paratype.

2. Cryptopora gnomon Jeffreys.

3a-c. Cryptopora maldivensis sp. nov., holotype. 4a-b. Cryptopora maldivensis sp, nov., paratype.

5. Cryptopora maldivensis sp. nov., paratype.

6. Cryptopora maldivensis sp. nov., paratype.

7. Cryptopora maldivensis sp. nov., paratype.

8. Dallithyris murrayi gen. et sp. nov.

9. Eucalathis murrayi (T. Davidson), syntype.

10. Eucalathis murrayi (T. Davidson), syntype.

11. Cryptoporal cf. boettgeri Helmcke.

12a-b. Leptothyris ignota gen. et sp. nov., paratype 13a-b. Leptothyris ignota gen. et sp. nov., holotype. 14. Leptothyris ignota gen. et sp. nov., paratype

! 2 6 JAN 1971 j

\ O,

BRITISH MUSEUM (NATURAL HISTORY)

THE

JOHN MURRAY EXPEDITION

1933-34

scientific Reports

VOLUME N, No. 1

THE PELAGIC TUNICATA

4

BY

R. B. SEYMOUR SEWELL. C.I.E., Sc.D., F.R.S.

(Lieut.-Colonel, I.M.S. [ret.])

WITH THIRTY-TWO TEXT-FIGURES AND ONE PLATE

LONDON :

PRINTED BY ORDER OF THE TRUSTEES

SOLD

B. Quaritch, Ltd., 11 Grafton Street, New H.M. Stationery Office, and AT

The British Museum (Natural History), Cromwell

1953

{Issued November 21th, 1953]

Mo/lt and printed in Gteal Britain

THE PELAGIC TUNICATA

BY

R. B. SEYMOUR SEWELL, C.I.E., Sc.D., F.R.S.

^ ~ V v

(Lieut.-Coloxel, I.M.S. [ret.])

WITH THIRTY-TWO TEXT-FIGURES AND ONE PLATE.

CONTENTS.

INTRODUCTION

Larvacea Acopa Doliolida Pyrosomida .

PAGE

1

3

8

45

55

INTRODUCTION.

In the following Report I have dealt with the Pelagic Tunicata obtained by the John Murray Expedition to the Indian Ocean, 1933-34. The collection is not a large one for the study of the Plankton was not one of the primary objects of the Expedition, and in consequence only relatively few hauls of the Plankton-nets were carried out with the object of ascertaining what differences in the fauna could be correlated with the observed changes in the physico-chemical conditions that prevail at different depths.

I give below a list of those species that were obtained :

Class LARVACEA (= APPENDICULARLE).

Order COPELATA.

Fam. Fritillariid^:.

Subfam. Fritillariin^:.

Genus Fritillaria Quoy and Gaimard.

Subgenus Acrocercus Lohmann.

Fritillaria ( Acrocercus ) formica Fol.

Subgenus Eurycercus Lohmann.

Fritillaria ( Eurycercus ) pellucida (Busch).

Fam. Oikopleurid^e.

Subfam. Oikopleurin^;.

Genus Oikopleura Mertens.

Subgenus V exillaria Lohmann.

Oikopleura (V exillaria) rufescens Fol.

0. (F.) dioica Fol.

X, 1.

1

2

JOHN MURRAY EXPEDITION

Class ACOPA (= CADUCICORDATA : THALIACEA).

Order SALPIDA (= DESMOMYARI A) .

Fam. Salpidae.

Group DoLiCHODAiA Metcalf.

Genus Cyclosalpa de Blainville.

Cyclosalpa pinnata (Forskal) var. seivelli Metcalf.

Group Polymaria Streiff.

Subgroup Sph asrod as A Metcalf.

Genus Salpa Forskal.

Salpa maxima Forskal.

S. fusiformis Cuvier.

S. cylindrica Cuvier.

Subgroup Circodala Metcalf.

Genus Ritteriella Metcalf (= Ritteria Metcalf).

Ritter iella amboinensis (Apstain).

Genus Metcalfina Ihle.

Metcalfina hexagona (Quoy and Gaimard).

Genus Iasis Lahille.

Iasis zonaria (Pallas).

Genus Thetys Blumenbach.

Thetys vagina Tilesius.

Genus Thalia Blumenbach.

Thalia democratica Forskal.

T. democratica var. orientalis Tokioka.

T. longicauda (Quoy and Gaimard).

Group Oligomyaria Streiff.

Genus Pegea Savigny.

Pegea confvedera.ta (Forskal).

Order DOLIOLIDA (= CYCLOMYARIA).

Fam. Doliolidae.

Genus Doliolum Quoy and Gaimard.

Subgen. Doliolina Borgert.

Doliolum ( Doliolina ) indicum Neumann.

Subgen. Dolioletta Borgert.

Doliolum ( Dolioletta ) gegenbauri Uljanin.

D. (D.) valdivice Neumann.

D. (D.) denticulatum Quoy and Gaimard.

THE PELAGIC TUNICATA

3

Order PYROSOMIDA.

Fam. Pyrosomatida;.

Genus Pyrosoma Peron.

Section Pyrosomata fixata Neumann.

Pyrosoma spinosum Herd man.

Section Pyrosomata ambulata Neumann.

Pyrosoma aheruiosum Seeliger.

P. verticillatum Neumann.

P. verticillatum, forma cylindricum Metcalf and Hopkins.

P. verticillatum. forma hyb idum Metcalf and Hopkins.

P. atlanticum (Peron).

Class LARVACEA.

Order Copelata.

Family Fritillapiid.e.

Genus Fritillaria Quoy and Gaimard.

Russell and Colman (1925, p. 227) have commented on the paucity of species of this genus in the collections made by the Great Barrier Reef Expedition, and they point out that in the records of the " Siboga Expedition to the Malay Archipelago they were by no means common. In the present collection only two species are represented, each by a single example. Aida (1907, p. 1), in his account of the Larvacea of the Japanese coast, has noted that in that region the species of the genus Fritillaria are always found in the swarms of Xoctiluca together with KowalevskiaP A similar condition was present at Sta. 58 off the South coast of Arabia, lat. 22° 22' 12" N., long. 59° 57' 30" E. on 5th November, 1933, when enormous numbers of Noctiluca were swarming in the surface water and among these were the only two examples of Fritillaria that have been seen.

Fritillaria pellucida (Busch).

Emycercus pellucida Busch, 1851.

Appendicularia furcata Vogt, 1854, p. 74, pi. x, figs. 1, 2.

Fritillaria furcata Fol, 1872, p. 32, pi. v, figs. 1, 2, pi. vi, figs. 1-3.

Fritillaria pellucida Lohmann, 1896, p. 32, pi. iv, figs. 1-7 ; Salensky, 1903, Pt. Ill, p. 99, pis. xii-xvi ; Aida, 1907, p. 5, pi. i. figs. 9-14 ; Ihle, 1908, p. 92, pi. ii, figs. 24-29, pi. iii, figs. 36, 45-47, pi. iv, figs. 48, 49, 58-66; Essenberg, 1926, p. 461, figs. 85-88; Lohmann, 1931, p. 145; Russell and Colman, 1935, p. 235 ; Harant, and Vernieres, 1938, p. 26, figs. 10, 41 ; Thompson, 1948, p. 66, pi. xix, fig. 4, pi. xx, figs. 1,2; pi. xxi, figs. 1, 2.

Occurrence : Sta. 58, South coast of Arabia, surface : 1 example.

Remarks. The body measures 0-75 mm. in length without the posterior processes, the width of the body is 0-26 mm. The length of the tail is about 1-20 times the length of the body, and its width is 0-31 of its length. The characteristic two pairs of large gland cells are present in the tail. The size of the specimen is small in comparison with examples from other regions. Busch, Yogt and Fol give the size of their examples as ranging from 1-8 mm. to as large as 3-0 mm. in length ; Ihle’s specimens from the Malay region measured 1-20 mm. in length, and Lohmann’ s examples were even smaller, measuring only 1-0 mm.

4

JOHN MURRAY EXPEDITION

while Thompson (1948) in South-east Australian waters obtained examples that ranged from 06 mm. to 2-2 mm. in length.

In spite of its small size the present specimen appeared to be sexually mature : both the ovary and testis were well developed and closely resemble the condition figured by Lohmann (1896, pi. iv, fig. 5) and Fol (1872, pi. v, fig. 1).

Distribution. This species is widely distributed throughout the warmer waters of all the great oceans.

Fritillaria formica Fol.

Fritillaria formica Eol, 1872, p. 35, pi. vii ; Lohmann, 1896, p. 41, pi. vi ; Ihle, 1908, p. 93; Essenberg, 1926, p. 481, figs. 119-124 ; Lohmann, 1931, p. 134, fig. 13 ; Haranfc and Vernieres, 1938, p. 20, fig. 38 ; Thompson, 1948, p. 58, pi. xvii, figs. 1-3, pi. xx, figs. 3, 4.

Occurrence : Sta. 58, South coast of Arabia, surface : 1 example.

Remarks. This specimen measures 0-63 mm. in body-length by 0-18 in breadth, and the tail measured 1*1 mm. in length. This is considerably smaller than the examples examined by Fol, in which the body measured 1-2 mm. and the tail 2-0 mm. Essenberg, however, obtained examples from the San Diego region that ranged in length of body from 0-4 mm. to over 1*0 mm.

Distribution. Like the preceding species, it is found in the warm regions of all the great oceans, and has also managed to penetrate into the waters of the West Wind Drift (Lohmann).

Lohmann (1931, p. 134, fig. 13) has figured two forms of this species f. digitata and f. tuber culata, but their geographical distribution appears to be identical. Both forms occur throughout the tropical region and both extend their distribution into the Antarctic region.

The two above species, Fritillaria pellucida (Busch) and F. formica Fol, appear to be hardy forms capable of existing in a wide range of temperature : Lohmann (1931) has recorded their occurrence in areas in which the surface temperature of the water was as high as 28-5-29-7° C. Essenberg seems to be doubtful whether they do actually exist in water with as high a temperature as this, and states that in the San Diego region the temperature range within which they were found was from 12-8° to 14-29° C. for pellucida, and from 12-3° to 14-5° C. for formica ; she points out that though Lohmann gives the surface temperature of the water at stations where catches were made, there is no means of determining whether the specimens actually came from this zone, since in most instances the tow-netting was made between the surface and some considerable depth. In the present case, however, there is no such doubt ; the examples were taken in the immediate surface water and the surface temperature was 26-7° C.

In the Siboga collections Fritillaria pellucida was taken in 17 stations and F. formica in 8 : they were the commonest species present in this region, and in the collections made by the Valdivia in the Indian Ocean they were the most common species between the Nicobar Islands and Ceylon, off the Seychelles, and again off the coast of East Africa in Lat. 1-6° S. They were the only species taken in the Gulf of Aden, so that their presence off the South coast of Arabia was to be expected. Lohmann and Buckmann (1926) have recorded the presence of these species as far south as Lat. 72° 20' in hauls from 200-0 m., and the second species, F. formica, in a haul with the closing net between 500 and 350 m.

THE PELAGIC TUNICATA

5

in lat. 54 : 29' S., long. 43' E. ; there can be little doubt that these examples had been carried south in the North Atlantic intermediate current from warmer regions.

O

Family Oikopleurid.e.

Genus Oikopleura Mertens.

Oikopleura dioica Fob

Oikopleura dioica Fol. 1872. p. 28, pi. iv, figs. 1—6 ; Lolimaim, 1896, p. 76, pi. xvi, fig. 1, pi. xvii, figs. 4, 9 ; Lohmann, 1901, p. 11 ; Aida, 1907, p. 19, pi. iv, figs. 7-11 ; Kruger, 1912, p. 26 ; Essenberg, 1926, p. 485, figs. 125-129 : Lohmann and Buehman. 1926. pp. 85. 145, figs. 17, 302, 33s and 342 ; Lohman 1831, p. 113; Berriil. 1950, p. 312, figs. Ill f. 112 d and 115; Harant and Yernieres, 193S, p. 37 ; Thompson, 1948, p. 37, pi. v, fig. 2, pi. vi, figs. 1-3.

Occurrence : Sta. 58, South coast of Arabia, surface : 9 specimens.

Remarks. As is so often the case, the present specimens appear to be relatively small ; their measurements are as follows :

Body.

Tail.

A

(

Length.

\

Depth.

r

Length.

Breadth

(mm.).

(mm.).

(mm.).

(mm.).

0-31

0-146

1-25

1 -25

0-383

0-187

1-33

0-2

0-52

0-24

1-53

0-2

Fol gives the length of his specimens as 1-00 mm. Lohmann obtained examples in Kiel Bight that measured 0-90 mm., and in the North Sea that were as large as 1-20 mm. : but he notes that occasionally he came across examples that were sexually mature but had a length measurement of only 0-3 or even 0-2 mm. Essenberg obtained examples in the San Diego region of the Pacific Ocean that ranged from 0-5 to over 1-0 mm. : she gives the length of the tail in her examples as being about 4 times the length of the body and its width as 0-17 of its length ; in the present examples the width of the tail was only 0-13 to 0-15 the length, but this smaller figure may be due to post-mortem shrinkage.

Distribution. This species appears to be a very hardy one. It has been taken throughout the warm regions of all three great Oceans, Pacific, Indian and Atlantic. Its temperature range is also wide ; Essenberg, cpioting from Lohmann (1896), gives its range as extending from 3-2° C. to 29-5° C. ; in the present instance the temperature in the surface layer in which it was taken was 26-7° C. Although usually taken in the upper layer above 200 m. depth, its ability to withstand low temperatures has enabled it in places to descend to much lower levels, and Lohmann (1896, p. 78) has recorded it from the Guinea Current in depths of 650-450 m. and 800-1000 m., the temperature in this last region being given as 5-2° C. Thompson (1948, p. 38) gives the range of temperature in which this species has been taken as 3-2° to 29-5° C.

The species possesses also a tolerance of a wide range of salinity, and Lohmann (1931, p. 114) has recorded it from the western end of the Baltio Sea in a salinity as low as OT%0 ; this tolerance enables it to exist in such estuarine regions as those of the Congo and Amazon rivers, while on the other hand it has been taken in the southern end of the Red Sea in

6

JOHN MURRAY EXPEDITION

water having a salinity of 36-95%0. It seems surprising that the species was not taken by either the Siboga Expedition to the Malay region or by the Great Barrier Beef Expedition.

Oikopleura rufescens Fob

Oikopleura rufescens Eol, 1872, p. 27, pi. x, fig. 3 ; Lohmann, 1896, p. 74, pi. xvi, figs. 2, 4, pi. xvii, figs. 1-3, 6 ; Salensky, 1904, pp. 45-98, pis. vi-x ; Aida, 1907, p. 17, pi. iv, figs. 1-6 ; Ihle, 1908, p. 114 ; Kruger, 1912, p. 26 ; Lohmann and Buckman, 1926, p. 24, figs. 16, 301, 337 ; Essenberg, 1926, p. 491, figs. 136-139 ; Russell and Colman, 1935, p. 220 ; Harant and Vernieres, 1938, p. 33, figs. 11, 25 ; Thompson, 1948, p. 35, pi. ii, fig. 4, pi. iv, figs. 2, 3, pi. v, fig. 1.

Occurrence : Sta. 58, South coast of Arabia, surface : several examples. Bemarks.— The size of the present specimens was as follows :

Body.

-A

Tail.

vV

r

Length.

Depth.

r

Length.

Breadth.

(mm.).

(mm.).

(mm.).

(mm.).

0-458-0-625

0-229-0-321

1-46-2-50

This is somewhat smaller than the sizes recorded by Essenberg of examples taken in the San Diego region, which attained a length of 1-5 mm. ; by Lohmann of examples from the Malay Archipelago which measured 0-653 mm. to 1-12 mm. in length ; and by Fol, who gave the length of his examples from the Mediterranean Sea as reaching as much as 1-8 mm. in length. Thompson (1948, p. 35) obtained examples ranging from 0-4 to 1-9 mm. in body length in South-east Australian waters. This species is a warm water form and has been recorded in temperatures ranging from 11-0° C. to 29-0° C.

Essenberg (1926, p. 494) states that this species has never been taken in depths deeper than 200 m. ; but Lohmann recorded specimens in a haul of the closing-net by the Plankton Expedition in the Atlantic Ocean between 1090 and 890 m., and by the Valdivia,” also in the Atlantic Ocean, between 550 and 250 m.

Class ACOPA (= CADUCICOBDATA : THALIACEA).

The presence of denticulations on the external surface of the test in a number of the pelagic Tunicates has been known for many years. Herdman (1888, p. 81) called attention to these structures in Sal/pa democratica (Forskal), and pointed out that at the base of each denticulation there is a small test-cell that is “in the process of becoming a bladder cell.” This denticulate condition of the test has been used by previous observers as a character for the separation of a new species, subspecies or variety in the Order Salpida : thus we have Salpa aspera Chamisso and S. echinata Herdman, both of which are now included as the forma aspera Chamisso of Salpa fusiformis Cuvier. Metcalf (1918) has described a variety of Salpa maxima, which he terms tuberculata, in which the aggregated zooid presents two thickened areas of the test which are covered with denticulations. In Thetys vagina Tilesius Herdman (1888) noted the presence of these small spines on the test of the solitary zooid and also of the form which he recorded as Salpa sp., which is now known to be the aggregated zooid of this species. Bitter and Byxbee (1905, p. 196) have recorded a similar denticulate condition of the test in certain specimens of the aggre- gated zooid of Pegea confoederata (Forskal) from the Pacific Ocean, and I have found a

THE PELAGIC TUNICATA

7

similar condition to be present in some examples of the solitary zooid from the Indian Ocean. In Thalia democratica (Forskal) denticidations are present along the processes that arise from the posterior region of the test and also around the margin of the oral and atrial apertures of the solitary zooid, and in many specimens of the aggregated zooid they form lines running along the length of the whole test ; in Metcalfina hexagona (Quoy and Gaimard) the posterior processes of the test in the solitary zooid are similarly denticulated. In Traustedtia midtitentacidata (Quoy and Gaimard) form bicristata of the solitary zooid the crests and the prominences at the two ends of the body are papillated, while in the aggregated zooid there is a large median postero-ventral pointed process, the surface of which is echinate and round the oral and atrial apertures the surface of the test is produced in a number of small papillae.

Similar small denticulations are to be found in the Pyrosomida ; they occur along the three or four ridges of the triangular or quadrangular process of the test that lies just ventral to the oral aperture of the zooid in Pyrosoma spinosum Herdman, and Metcalf and Hopkins (1919, p. 2G1) have called attention to the presence of similar denticulations or papillae at the tip of the processes of the test that overhang or surround the oral aperture in other species of Pyrosoma, namely P. ovatum Neumann and P. atlanticum (Peron). They remark, outside the truncate surface, the tip of the oral test process bears numerous minute denticles, at the base of each of which lies a test cell, which doubtless either secretes the test material of which the denticle is composed, or so influences its arrangement that it takes the form of a denticle.

These test cells are mesenchyme cells, which have wandered outside the zooids in which they arose, have migrated to a distance, and have each taken up a definite position in the test at a distance from the zooids, there to form or control the formation of a denticle.” In a previous paper (Sewell, 1926, p. 77) I have pointed out that it seems impossible to justify any separation, even as a distinct form, of those with a spinose test from those with a smooth one, though it is possible that Ritter and Farran are right in their belief that the spinose character is a mark of age.” Farran (1906, p. 11) agrees with Ritter that in the case of Salpa fusiformis these denticulations are a mark of age, aspera being an older stage than the smooth fusiformis. Apstein (1894, p. 13) considered that it was in younger examples of Thalia democratica (Forskal) that these denticulations were to be found, but in my experience such a condition of the test may occur at any age up to mid- life, after which they tend to be eroded away. In the species Pyrosoma atlanticum (Peron) the examples in the present collection exhibit a gradual increase, following a rather late start, in the number of these small denticulations or papillae with an increase in size and presumably of age of the colony ; in the smallest examples there were no such papillae either on the surface of the test or around the lips of the oral aperture ; in somewhat larger examples they are present on the lips of the oral funnel, and in the larger examples they are seen scattered over the surface of the test ; thus in this instance these papillae would seem to be a mark of age and not of youth in a colony.

I also (loc. cit., p. 65) suggested that in view of the great degree of plasticity that is found in the Salpida, to which Metcalf (1918) has called attention, and the periodic and rhythmic changes in the environmental conditions to which individuals are exposed in Indian waters (changes that may be so sudden and so great that they cause the death of many individuals), the final result may be the production of a number of variations, using this term in its widest sense.

8

JOHN MURRAY EXPEDITION

Garstang (1933) has also put forward the view that such differences in the environment may have induced modifications in the development of certain species among the Doliolida, and that this has led to the creation of so-called species that are actually only modi- fications of a single species : and from my study of the Pyrosomida in the present collection I have come to the same conclusion, and regard a number of so-called species as stages in the gradual development of the colony (vide infra , pp. 57 et seq.).

Class ACOPA (= THALIACEA).

Order SALPIDA (= DESMOMYARIA).

Family Salpid^e.

Group Dolichod^a Metcalf.

Genus Cyclosalpa de Blainville.

Cyclosalpa pinnata (Forskal) var. seioelli Metcalf.

Cyclosalpa pinnata Metcalf, 1918, p. 9, figs. 1-14, pi. i, figs. 1, 2, pi. ii, fig. 5 ; Sewell, 1926, p. 68, figs. 1-4 ; Stiasny, 1927, p. 414, fig. a, pi. xx; Ihle, 1927, p. 24; Tokioka, 1927, p. 219; Russell and Colman, 1935, p. 210; Harant and Vernieres, 1938, p. 33, figs. 2, 12 and 26 ; Thompson, 1948, p. 108, pi. xxxii, pi. xxxiii, figs. 1-4, pi. xxxiv, figs. 1-3.

Cyclosalpa pinnata sewelli Metcalf, 1927, p. 257.

Salpa proboscidialis Lesson, 1830, p. 25, pi. xxxiii, figs. 2, 2a.

Occurrence : Sta. 96, Central part of Arabian Sea, 10 m. depth ; few examples of the solitary form.

Remarks.- These examples agree with the form which I recorded in a previous paper (Sewell, 1926), and which differs from the typical form in having, instead of the usual five, only four luminous organs between muscles II and VI, that between muscles I and II being absent.

The oral musculature agrees exactly with the description given by Metcalf (1918). Distribution.- This species is widely distributed throughout the great oceans in the tropical and temperate regions. Up to now the variety seivelli has only been recorded from the Indian Ocean.

Group Polymyaria Streiff.

Subgroup SPHyERODiEA Metcalf.

Genus Salpa Forskal.

Salpa maxima Forskal. (Text-fig. 1.)

Salpa maxima Streiff, 1908, p. 21, figs. 9-14 ; Metcalf, 1918, p. 83, figs. 64-72 ; Sewell, 1926, p. 83 ; Stiasny, 1927, p. 419, fig. c, pi. xxi, figs. 13-15 (solitary zooid), 16-18 (aggregated zooid) ; Tokioka, 1937, p. 223 ; Harant and Vernieres, 1938, p. 40, figs. 52, 61 ; Thompson, 1948, p. 154, pi. lxviii, figs. 1, 2, pi. lxix, figs. 1-6.

Occurrence :

Sta. 46, South coast of Arabia, surface : 3 examples of the aggregate zooid.

Sta. 95, Central part of Arabian Sea, 984-430 m. : 3 examples of the solitary zooid, 17 examples of the aggregated zooid.

Remarks.- Of the three examples of the solitary zooid taken at Sta. 95, two were normal in structure : but in the third example the 1st and Ilnd body-muscles are united

THE PELAGIC TUNICATA

9

u2

Ui

L

2

Text-fig. 1. Sal pa maxima Forskal. Aggregated zooid, showing an abnormal arrangement of the

oral musculature.

together in the mid-dorsal line by some of the fibres from the right part of body-muscle I being continued across the dorsal line into the left part of body-muscle II.

Aggregated zooid : With a single exception, taken at Sta. 46, all the present specimens belong to the variety tuberculata Metcalf. The average proportional lengths of the body and the two, anterior and posterior, processes are as follows :

Sta. 46

Sta. 95

Average

Anterior

process

(mm.).

30

41

47

35

35

24

35

53

35-7

Body

(mm.).

43

56

63

52

55

56

64 73

57-75

Posterior

process

(mm.).

25

24

42

30

30

35

20

24

28-75

Thus the average total length, including both the anterior and posterior processes, is 124 mm. ; this is considerably larger than the example figured by Metcalf (1918, fig. 72) which appears to have had a total length of about 66 mm. The two thickened and spinose areas of the test agree with Metcalf’s description.

10

JOHN MURRAY EXPEDITION

According to Metcalf the musculature of this variety agrees with that of the typical form ; but in two examples of the present collection that I carefully examined there is an interesting variation in the oral musculature. So far as I could determine, the 1st sphincter muscles in both the upper and lower lips arise from a small common retractor, that overlies but does not join the main oral retractor muscle, which divides anteriorly into the Ilndand Illrd sphincters of both the upper and lower lips. The anterior fibres of the Illrd sphincter of the upper lip (U3) are continued across the angle of the mouth and curl forwards and downwards to join the Ilnd sphincter of the lower lip (L2). All the sphincter muscles are complete except the 1st sphincter of the upper lip, which is interrupted in the mid-dorsal line. This arrangement of the oral muscles corresponds closely with the arrangement found in the solitary zooid (vide Streiff, 1908, pi. i, fig. 9), except that the portion of the oral retractor muscle, which Streiff labels za, is markedly reduced, and does not appear to join the main retractor muscle but lies just dorsal to its commencement, where the Illrd upper and lower sphincter muscles turn back to form the main mass of the retractor. Below the oral retractor muscle the intermediate muscle ( i.m .) divides into anterior and posterior branches (Text-fig. 1).

In the other specimens the arrangement agrees with the description given by Streiff (1908, p. 22). The oral retractor muscles consist of two parts : the upper divides into three branches and forms the 1st upper ( U-d) and the 1st and 2nd lower (L1 and L2) sphincters while the lower part forms the 2nd and 3rd (U2 and U3) upper sphincters and the 3rd lower (La)-

Distribution. This species appears to be rare in eastern waters. Apstein (1906a, p. 266 and fig. 4) has given a map showing its occurrence in the great oceans, and records only two catches in the eastern part of the south Pacific and another off Cape Horn. Tokioka (1937) has noted that Oka recorded its presence in Japanese waters, but states that he has never seen any examples from this locality. Metcalf (1918, p. 83) gives a number of records of the capture of this species in the region of the Sulu Archipelago and the Philippine Islands, all of them being from the surface waters. Thompson (1948, p. 156) states that it is of relatively common occurrence in the south-east Australian region, though the numbers taken vary from year to year, and was most common in the middle of the Tasmanian Area. Neither the Siboga nor the Great Barrier Beef Expedition obtained examples in the south-west Pacific region and the Malay Archipelago, and the Valdivia only obtained a few examples of the solitary zooid in the region to the north- east of New Amsterdam Island in the south-east part of the Indian Ocean. The Valdivia” report unfortunately gives no indication of the actual depth at which these specimens were captured ; they were taken in vertical hauls between 1800 and 2500 m. and the surface. I have recorded the occurrence of two examples of the aggregated zooid in a haul at Investigator Station 682 in the Laccadive Sea from 700 fathoms (1280 m.) to the surface. The present records from the Arabian Sea indicate that this species may occur at considerable depths, for 3 solitary and 17 aggregated zooids were taken in the self-closing net between 984 and 430 m. depth.

Salpa fusiformis Cuvier.

Salpa fusiformis Ihle, 1912, p. 39, figs. 37-40 ; Metcalf, 1918, p. 88, figs. 73-81 ; Sewell, 1926, p. 75 ; Stiasny, 1927, p. 424, text-fig. d, pi. xxi, figs. 19-21 and 22-24 ; Ihle, 1927, p. 26, figs. 4, 5 ; Harant and Vernieres, 1938, p. 42, fig. 60 ; Thompson, 1948, p. 156, pi. lxx, figs. 1, 2, pi. lxxi, figs. 1-5 ; Berrill, 1950, p. 293, figs. 104d, f and i, and 106.

THE PELAGIC TUNICATA

11

Occurrence : Sta. 61. dav, Northern area of Arabian Sea, 1000-0 m. : 2 examples, aggregated zooid.

OO O

Remarks. These examples were very small, measuring only 3-5 mm. in length. Distribution. This species occurs in the warmer regions of the Pacific, Indian and Atlantic Oceans, and may occasionally be carried into higher latitudes. It has been recorded from about 60 X. in the Atlantic and 6 1 S. in the southern part of the Indian Ocean.

Salpa cylindrica Cinder.

Salpa cylindrica Metcalf. 1918, p. 93, figs. 82-89 : Sewell. 1926. p. 77, figs. 7-13 ; Stiasny, 1927, p. 429, fig. e. pi. xxii. figs. 25-30; Tokioka, 1937. p. 223: Russell and Dolman, 1935, p. 217 ; Thompson, 1948. p. 161. pi. lxxii. figs. 1, 2, pi. lxxiii, figs. 1-5.

B

Text-fig. 2. Salpa cylindrica Cuvier. Solitary zooid. a, Side view of an individual possessing ten body-muscles. B, The atrial retractor of the right side.

Occurrence : Sta. 7, Red Sea, 100-0 m. : large numbers of the solitary zooid.

Sta. 61, Northern area of Arabian Sea, 1000-0 m. : 2 aggregated zooids.

Sta. 95, Central part of Arabian Sea, 984-430 m. : 23 solitary and 9 aggregated

zooids.

1

Sta. 172, Central part of Arabian Sea, 200-0 m. ; 1 solitary zooid: 850-0 m., 1 aggregated zooid.

Remarks. Solitary zooid : The specimen from Sta. 172, 200-0 m. depth, is interesting, for it exhibits the variation in the oral musculature to which I called attention in a previous paper (Sewell, 1926, p. 79, fig. 9). The oral retractor gives off two sphincter muscles to each lip and in this instance all four are continuous across the middle line. There is also an additional body-muscle present, the total number being 10, instead of the more usual 9, and the Xth muscle-band divides below the level where it crosses the atrial retractor

12

JOHN MURRAY EXPEDITION

into a short stout anterior branch and a somewhat longer and more delicate posterior branch, exactly as Metcalf (1918, fig. 82) has figured for muscle IX. The atrial retractor crosses the Xth body-muscle and extends forwards for some distance but not as far as the IXth muscle. Just behind the Xth body muscle the atrial retractor is crossed by a moderately strong complete muscle-band, which in the lateral line bends forwards and comes into contact with the Xth body-muscle.

After a short course the atrial retractor commences to divide and gives off bundles of fibres which arise from the upper or dorsal border of the muscle and pass alternately ventrally and dorsally, as shown in Text-fig. 2b. There are eleven such muscle strands, and the most distal muscle of the atrial aperture is a delicate complete muscle strand that is not connected with the retractor.

This arrangement appears to differ from the account given by Streiff (1908), and copied by Metcalf, of the atrial musculature in both Salpa maxima and S. fusiform, is ; they show the dorsal muscle-bands arising from the atrial retractor muscle and the ventral bands crossing the atrial retractor on the outside and ending independently of it ( vide Streiff, 1908, pi. I, fig. 10, and pi. ii, fig. 15).

Aggregated zooid : The examples of the aggregated zooid were very small and measured only about 7‘0 mm. in total length. They appear to agree with the description given by Metcalf (1918).

Distribution. This species has been recorded from the tropical region of all three great oceans, Pacific, Indian and Atlantic. It is possible that by the movement of the great water masses examples may be carried into colder regions. In order to account for the occurrence of specimens in such areas as Lat. 46° S. off Prince Edward Islands and lat. 52° S. off Kerguelen, from which, according to Herdman (1888, p. 72), the Challenger obtained single specimens in bad condition ”, Apstein (19066, p. 266) points out that through the Mozambique Current salps might be carried from the tropical area into the West Wind Drift and so be swept eastward : but the fact that these examples in the Challenger collection, always assuming that Herdman’s diagnosis was correct, were in bad condition, suggests that they were dead and decomposing at the time of their capture.

Thompson (1948) reports that in the South-east Australian area it is limited to the more northerly regions ; Russell and Colman (1935) record it from the region of the Australian Barrier Reef, but it was not an abundant species.”

Subgroup Circodea Metcalf.

Genus Ritteriella Metcalf.

Ritteriella amboinensis (Apstein). (Text-fig. 5a and c).

Salpa amboinensis Apstein, 1904, p. 651, figs. 2-10 ; Ihle, 1910, p. 34, pi. i, figs. 7, 8 ; Ilile, 1912, p. 44,

figs. 45-47.

Ritteria amboinensis Metcalf, 1918, p. 56, figs. 29, 30 ; Sewell, 1926, p. 85, figs. 15, 16.

Ritteriella amboinensis Ihle, 1935, p. 528 ; Thompson, 1948, p. 126, pi. xlvi, figs. 1, 2, pi. xlvii, figs. 1-4,

pi. xlviii, figs. 1, 2.

Occurrence : Sta. 96, Central part of Arabian Sea, 10 m. depth : a few solitary zooids.

Remarks. I have in a previous paper (Sewell, 1926) pointed out that both the oral- and body-muscles of the solitary zooid vary in different individuals. In one example in the body-muscles, of which Metcalf (1918, fig. 30) figures eleven in his specimen, the

THE PELAGIC TUNICATA

13

anterior three meet in the mid-dorsal line : the Illrd left, muscle divides in the mid-dorsal line and