REPORT ON THE TUNICATA. 135 



restricted genus. Macleay, in 1823, separated Styela from Savigny's genus Cynthia, but 

 this division was not accepted by other writers, and the term Cynthia continued to be 

 used in the old sense until Heller, in 1877, 1 defined the four genera — Microcosmus, Styela, 

 Polycarpa and Cynthia, using the latter in the restricted sense in which it is employed 

 here. 



A genus Cynthia was founded by Thompson subsequently to Savigny's ' : Memoires," 

 for a small group of Schizopodous Crustaceans allied to Mysis. Even although Cynthia 

 is not now employed strictly as denned by Savigny, still it includes the most typical forms 

 of Savigny's genus, and as it is generally recognised and accepted, there is no doubt that it 

 ought to remain. There is more chance of confusion arising from the substitution of 

 Halocynthia, as proposed by Verrill, than from the employment of the same generic name 

 in a totally distinct class of animals. 



Traustedt 2 admits the distinctness of Styela from Cynthia, but does not, however, 

 accept Heller's Microcosmus. Hence Traustedt employs Cynthia in rather a wider sense 

 than that in which it is used here. 



The characters of Cynthia are those of the sub-family, with the exception of the 

 features which distinguish Microcosmus. The body may vary greatly in shape, but is 

 always attached, is very rarely stalked at all, and has never a long peduncle. The 

 branchial and atrial apertures are both either scpiare or surrounded by four lobes. The 

 test is usually leathery; it may be thin but is always tough. Occasionally it is soft and 

 cartilaginous, but never so much so as in the genus Ascidia. There are no hairs developed 

 upon the outer surface, 3 and there is almost never an incrusting coat of sand. The 

 mantle is usually very thick, and has the muscle bands strongly developed, forming two or 

 three distinct layers. 



The branchial sac is thrown into a series of strongly-marked folds, usually six or seven 

 on each side, but more may be present (there are eleven upon each side in Cynfln'o 

 complanata, and twelve upon each side in Cynthia grandis). 



The condition of the dorsal lamina is one of the characters upon the strength of 

 which Heller separated Microcosmus from Cynthia. In the latter genus the dorsal 

 lamina has its free edge bordered by a series of short languets, while in Microcosmus it is 

 a plain membrane. The tentacles are compound, and they do not differ appreciably from 

 those of Microcosmus, or of the Bolteninae. 



The alimentary canal is usually large, and the stomach is distinct ; the intestine forms 

 a wide loop. The genitalia have various forms, but are developed upon both sides of the 

 body, and are usually simple or lobed elongated masses. 



The Challenger collection contains nine species of Cynthia, eight of which are new 



1 Untersuch. ii. d. Tun. d. adriat. und Mittelm., Abth. 3, Th. 1, Denkschr k. A_kad. Wis* nseh. Wien, Bd. xxxiv. 



2 Oversigt over de fra Danmark, &c, Aseidia' Simpliees, viil. Miil.l. Nat. I'm-., Kjobi-nliavn, ls80. 



3 Except upon Cynthia hispida and the anterior end of Cynthia formosa. 



