60 DISCOVERY REPORTS 



Gut. The oesophagus is narrow and the stomach (st.) large with a somewhat rectangular outline. 

 The post-stomach is generally quite long and conical, but is sometimes short. The intestine is short 

 and narrow. The rectum is wide at its lower end but soon narrows. The narrow part is bent into an 

 S-shaped curve. The anus, which is situated at the base of the thorax, opposite the 4th row of stig- 

 mata, has two shallow lips. 



Gonads. The testis (t) is undivided and the sperm duct makes three spiral turns round it. In some 

 colonies only the ovary was developed. 



Remarks. D. trivolutum somewhat resembles two other species from South American waters, 

 D. tenue (Herdman) and D. chilense Arnback. The characters which most readily separate D. tri- 

 volutum are listed in Table 17. In this comparison the characters of D. chilense were taken from 

 Arnback (1929, fig. 5), and the diameter of the spicules of D. tenue was measured in specimens of 

 Herdman's original material kindly lent by the British Museum (Natural History). 



It will be seen that D. tenue and D. chilense are not distinguished from each other by the characters 

 listed. But Arnback, having compared material of the two species, was satisfied that, in spite of 

 similarities 'the differences are more essential, lying in the form of the zooids, which are not very 

 elongated but larger in the species tenue, having a short atrial languet, a longer and more sharply 

 curved intestinal loop '. 



Table 17 



D. trivolutum D. tenue D. chilense 



Spicules Up to 40 /a in diameter Up to 25 /i in diameter Up to 26 in/x diameter 



Lateral thoracic organs Large ; placed half-way along thorax Small ; placed at posterior end Not described 



of thorax 



Sperm duct 3 spiral turns Unknown 6-7 spiral turns 



Genus Leptoclinides Bjerkan, 1905 



This genus was characterized by Bjerkan as having four rows of stigmata and a backwardly directed 

 funnel-like atrial siphon. Van Name (1945) suggested that it should be no more than a subgenus of 

 Didemnum, and Carlisle & Carlisle (1954) gave reasons for dividing the species hitherto assigned to 

 Leptoclinides among other genera of the Didemnidae, while retaining Leptoclinides as a subgenus of 

 Didemnum. I believe, however, that the well-developed funnel-like atrial siphon clearly distinguishes 

 Leptoclinides from Didemnum, no species of which shows any tendency towards the production of an 

 atrial siphon. 



Leptoclinides diemenensis Michaelsen (Text-fig. 13) 



Leptoclinides diemenensis Michaelsen, 1924, p. 331, fig. 12. 



Occurrence. St. 935 : North Island, New Zealand, 84 m. 



Colony. The colony is about 3 cm. long and 07 cm. in thickness. It is pale orange brown in 

 colour. The upper surface has a number of low rounded swellings, each with a common cloacal 

 opening at its centre. These openings are less than 1 mm. in diameter and are spaced about 5 mm. 

 apart. Around each opening is an irregular system of closely spaced zooids. The colony is firm and its 

 surface smooth. 



Sections show that the uppermost layer of the common test is composed largely of closely pressed 

 bladder cells, each about 70-80 ft in diameter and extending to about five cells in depth. Below these 

 is a layer of densely packed spicules. Spicules are also present in the deeper parts of the common test, 

 but are more scattered. The spicules are generally 20-35 fi in diameter, only a few reaching 40 fi. 





