4 Dr. Asajiro Oka: 



It will be seen at once from the above diagnosis that the 

 present genus exhibits in certain essential points a close relation- 

 ship to the Pyrosomidae, while in other characters no less 

 important it markedly approaches the Distomidae (Polycitoridae) 

 among the compound ascidians. It agrees with Pyrosoma, on the 

 one hand, not only in the form and general appearance of the 

 colony already referred to, but also in the structure of the alimentary 

 canal, which is practically the same in both forms. On the other 

 hand, the presence of numerous bladder cells in the test naturally 

 reminds of the condition found in the genera Colella (=:Sycozoa) 

 and DistapUa (^Holozoci) among the Distomidae (Polycitoridae), 

 in some members of which these cells form by far the greater part 

 of the investing mass. The stalk, too, much resembles that of 

 some species of the genus Colella. e.g. C. quoyi ; but this is unim- 

 portant, as similarly stalked forms are also met with in some other 

 families. 



One of the most notable jDoints about this form is without 

 doubt the partial fusion of the peribranchial cavities in a number 

 of zooids. So far as I am aware, there is but one member of the 

 Ascidiae compositae in which all the zooids exhibit a similar 

 structure. According to Lahille ('90), the zooids of Diplosomoides 

 lacazei (= Polysyncraton /.) have their peribranchial walls very 

 imperfectly developed so that the greater part of the branchial 

 sac is uncovered. Since other species of the genus do not 

 present the same condition, this character ought to be looked 

 upon as simply specific. In the present family, however, of 

 which no other genera or species are known yet, it must be left 

 doubtful whether this peculiarity should be regarded as a family 

 character or as of only generic or even specific importance. 



This genus contains the single species C. miraUlis. 



Cyathocormus mirabilis nov. sp. 



The colony is cup-shaped and is attached by the base of a 

 short peduncle. The head has the form of a short hollow cylinder 

 nearly as long as it is wide. The outer surface shows a number of 



