72 
\ 
THE YOYAGE OF H.M.S. CHALLENGER. 
Distomid^. 
No internal longitudinal 
bars in branchial sac. 
Colony provided with a Colony sessile or scarcely 
well-marked peduncle. pedunculated. 
Branchial sac provided 
with internal longi- 
tudinal bars. 
I 
Symplegma. 
No incubatory An incubatory 
pouch present. pouch present. 
I Colella. 
Ascidiozooids 
not completely 
imbedded in a 
common test. 
Ascidiozooids 
completely 
imbedded in a 
common test. 
Chondrostachijs. 
Oxycorynia. 
An incubatory No incubatory 
pouch present. pouch present. 
Distajplia. I 
Ascidiozooids 
enclosed hy 
calcareous 
capsules. 
Ascidiozooids 
not enclosed by 
calcareous 
capsules. 
Cystodytes. 
Distoma. 
Of these seven genera, four are represented in the Challenger collections, viz., Colella, 
Distaplia, Cystodytes, and Symplegma. 
Of the three remaining genera, Chondrostachys was described by Dr. J. Denis 
Macdonald in 1858 from a specimen found in Bass Strait, Australia; it has not, so far 
as I am aware, been rediscovered. It is a peculiarly interesting form, since it 
approaches Diazdna and the Clavelinidse in the partial independence of the Ascidiozooids. 
Oxycorynia was formed by Dr. E. von Drasche in 1882 for a species from the Caroline 
Islands. It is closely related to the new genus Colella. Distoma, finally, is the oldest 
and best known member of the family. It is distinguished superficially from the other 
genera by forming large massive generally sessile colonies. 
Colella, n. gen. 
Colony more or less club-shaped, and composed of a peduncle attached at the 
base and bearing on its summit a more or less ellipsoidal head. 
Ascidiozooids imbedded in a common test, usually arranged in lines but not 
divided into systems. No common cloacal cavities visible. Body composed 
of thorax and abdomen and a long ectodermal process from the posterior 
end of the latter. Apertures six-lobed, not prominent. 
Test gelatinous, penetrated by ectodermal prolongations from the Ascidiozooids. 
Branchial Sac well developed ; no internal longitudinal bars present. 
Dorsal lamina composed of languets. 
Alimentary Canal posterior to the branchial sac. 
Reproductive organs placed on the left side of the intestinal loop. Testes grape- 
like in arrangement. Embryos develop in an incubatory pouch. 
