REPORT ON THE TUNICATA. ■ 87 



1827. Of the synonyms given above, Thalia is pre-Linuean, and Holothuvia is pre- 

 occupied, while Salpa has been appropriated by the more important section of the family. 

 Orthoccela, Macdonald, is a better designation, but must yield priority to Cyclosalpa. 



By the majority of authors since the time of Blainville, Cyclosalpa pinnata has 

 been placed as a species of Salpa, but Macdonald^ in 1864 founded for it the new 

 genus Orthoccela, on account of the straight condition of the alimentary canal, 

 which forms a marked contrast to the coiled-up visceral mass found in the species 

 of Salpa. Traustedt, though not recognising this as a separate genus, makes it a 

 distinct section of Salpa. 



The characters of the genus agree with those of Salpa, with the exceptions of 

 (1) the extended condition of the alimentary canal, and (2) the curious form produced 

 by the animals of the aggregated generation which are united to form, not a ribbon-like 

 chain as in the species of Salpa, but a ring or circlet of generally about nine members. 



This genus contains three species, viz.: — 



Cyclosalpa pinnata, Forskahl ; Cyclosalpa affinis, Chamisso ; and Cyclosalpa 

 dolicosoma-virgula, Todaro — Vogt. 



Cyclosalpa pinnata (Forskahl). 



Salpa pinnata, Forskahl, Descr. Anim., p. 113, 1775. 



Orthoccela pinnata, Macdonald, Trans. Eoy. Soc. Edin., vol. xxiii. p. 171, 18G4. 



Salpa pirmata, Traustedt, loc. cit., p. 353, which see for further synonymy. 



This is the only species of the genus in the Challenger collection, and it is only 

 represented by a single specimen of the solitary generation, obtained on the surface of 

 the Pacific between Papua and Japan. It measures about I'S cm. in length, and is 

 not in a very good state of preservation. 



Family II. Octacnemid.^. 



Body flattened antero-posteriorly (?), probably attached. 



Test gelatinous, thin, transparent. 



Branchial Sac with no stigmata or openings into the peribranchial cavity. 



Alimentary Canal placed dorsally and posteriorly. Coiled up along with the 



reproductive organs to form a visceral mass. 

 Life-History unknown. 



This family is formed for the reception of the remarkable Octacnemus hythins, which 

 was discovered by the Challenger Expedition, and was first described by Professor 



' The genus Pyrosomopsis established at the same time by Macdonald is apparently the aggregated condition of a 

 Cyclosalpa. 



