26 Cyathocormus mirabilis n. g., n. sp. 



tion of a compound ascidian, but it should certainly be taken into 

 consideration when it is so highly specialised as in the present 

 species. It is in fact one of the chief diagnostic characters by 

 which the family Cyathocormidae differs from all the other 

 recognized families of the Ascidiae compositae. 



The hollow cylindrical form of the colony of Cyathocormus is so 

 utterly different from that of other compound ascidians that it 

 seems at first sight almost impossible to reduce it to one of the 

 typical forms of colony prevalent among these animals. On the 











•^ r 



^v^ 



Text-tig. 4. Text-tig. 5. Text-tig. 6. 



Coelocormiis C tjathocormus Pijrosovia 



contrary, its extraordinary shape recalls the arrangement seen in 

 Fyrosoma, where the zooids and their investing mass form the walls 

 of a hollow cylinder closed at one end. As shown in the 

 accompanying woodcuts (text-figs. 4, 5, and 6) the mode of ar- 

 rangement of the zooids is practically the same in Cyathoconmis 

 (text-fig. 5) and Pyrosoma (text-fig. 6), whereas in Coelocorimis (text- 

 fig. 4), which was considered by Prof. Herdman to be the most 

 Pyrosoma-]ike compound ascidian, the arrangement is quite 

 different. Here the whole surface, both the outside of the colony 

 and also the lining of the axial cavity, is morphologically the 

 outer surface, and the branchial apertures of the zooids are found 

 distributed all over it. It is therefore evident that although the 

 form of the colony in Coelocormiis huxleyi somewhat resembles that 

 of Pyrosoma, still the inner surface lining the central cavity is 

 homologous with part of the outer surface of an ordinary compound 



