EEPOET ON THE TUNICATA. 239 



another. Clavelina and Ecteinascidia, though differing so decidedly in the structure of 

 the branchial sac, are rather more closely allied than is either of them to Perophora, which 

 agrees, however, with Clavelina in the absence of internal longitudinal bars. In the 

 shape of the branchial sac, and its relations to the viscera, Peropltom may be compaivi] 

 to Ascidia, while Ecteinascidia and Clavelina represent dona amongst the Ascidiidae ; 

 even in Perophora, however, the intestine sometimes extends slightly beyond tin- branchial 

 sac posteriorly. 



These three genera may be distinguished briefly thus : — 



Clavelinidj:. 



Branchial sac having internal Branchial sac having no internal 



longitudinal hars. longitudinal bars. 



Ecteinascidia 



Intestine extending beyond Intestine at side of bran- 



the branchial sac, so as to chial sac; no abdomen, 



form an abdomen. 



Clavelina. Perophora. 



The Challenger collection contains two species of Clavelina, and three other forms 

 which necessitated the formation of the genus Ecteinascidia. Perophora is not 

 represented. 



Ecteinascidia, Herdman. 



Ecteinascidia, Herdman, Prelim. Rep., Proc. Eoy Soc Edin., 1879-80, p. 722. 



Body oblong, usually tapering posteriorly. Apertures indistinctly lobed. 



Test cartilaginous or membranous. 



Mantle thin, musculature moderately strong. 



Branchial Sac having internal longitudinal bars, but no papillae; stigmata 



straight. 

 Dorsal Lamina in the form of languets. 



Tentacles simple. 



Viscera extending beyond the branchial sac posteriori}". 



This genus was formed for the reception of three new species of colony-forming 

 Simple Ascidians, with non-papillated internal longitudinal bars in their branchial sacs. 

 This character distinguishes them from both Perophora and Clavelina, and necessitated 

 the formation of a new genus. 



