186 THE VOYAGE OF H.M.S. CHALLENGER. 



The Challenger collection contains representatives of all these genera, with the 

 exception of Rhodosoma and Chelyosoma. Four of the remaining seven, namely, 

 HypobytMus, Pachychlcena, Abyssasddia and Corynascidia have been founded for the 

 reception of new forms obtained during the expedition. 



Corynascidia, n. gen. 



External Appearance. — Shape elongated, pyriform, pedunculated ; apertures not 



lobed. 

 Test gelatinous or membranous. 

 Branchial Sac extremely delicate. Internal longitudinal bars present, but not 



provided with papillae. Interstigmatic vessels coiled spirally. 

 Dorsal Lamina in the form of languets. 

 Tentacles simple, filiform. 

 Viscera on dorsal edge of branchial sac, running antero-posteriorly. 



This curious genus is closely allied to Corella, but is so different from it in many 

 particulars as to necessitate the formation of a new genus. Its greatest peculiarities are 

 the pyriform pedunculated body, the delicate spirally coiled vessels in the branchial sac, 

 and the form and position of the viscera, Further remarks on its structure and affinities 

 will be given at the end of the description of the single species known. 



Corynascidia suhmi, n. sp. (PI. XXV.). 



External Appearance. — The shape is pyriform, and consists of a body which is flat- 

 tened laterally, and a long stalk. The body is elongated, and the anterior and dorsal 

 ends are short, while the ventral and posterior are greatly elongated, so as to produce a 

 triangular shape. The stalk is about as long as the bod)-, and is very thin where it joins 

 the bod)' at the ventral edge of the posterior end. It gradually iucreases in width as it 

 runs backwards, till at the point of attachment it is three times its original breadth. The 

 apertures are not lobed ; they are rather wide, and slightly projecting ; the branchial is 

 at the ventral edge of the anterior end, and is directed anteriorly and ventrally ; the atrial 

 is at the dorsal edge, and is directed dorsally. There is a deep depression in the middle 

 of the dorsal edge, just opposite the stalk. 



The surface is smooth and pretty even. Some parts of the body are finely creased 

 longitudinally. The surface of the stalk is smooth and glistening. The colour is dirty 

 grey, with a yellowish tinge on parts of the body. 



Length of the body (dorso-ventral), 7 cm.; breadth of the body (antero -posterior), 3'2 

 cm.; length of the stalk, 7 '5 cm. 



