610 PEor. w. A. herdmak's eevised 



Ascidiozooids of moderate length, and having the body divided 

 into two regions, thorax and abdomen ; thej may be provided 

 with long vascular ectodermal appendages. 



Test gelatinous or cartilaginous, often thickened at tlie base to 

 form a peduncle, which may be traversed by large canals contain- 

 ing the vascular appendages of the ascidiozooids. There are 

 sometimes calcareous spicules, which, however, are not stellate. 



SrancMal sac well developed ; no internal longitudinal bars 

 present. 



Dorsal lamina represented by a series of languets. 



Alimentary canal placed posteriorly to the brancbial sac, so as 

 to form an abdomen. 



Gonads and heart in tlie intestinal loop, or alongside it. Sper- 

 matic vesicles numerous, vas deferens straight. 



The genera in this family may be separated as follows : — 



/ Colony with a well-marked peduncle 1 



\ Colony sessile or only shortly pedunculated 2 



-J [With an incubatory pouch in which embryos develop Colella. 



I No incubatory pouch present 3 



(Ascidiozooids completely imbedded in a common test. . Oxycorynia. 

 Ascidiozooids not completely imbedded in a common test. 

 Chondrostachys. 



o f With an incubatory pouch and an atrial languet Distaplia. 



"^ \ No incubatory pouch present 4 



[ Ascidiozooids enclosed by capsules formed of discoid spicules. 

 4 \ Cystodytes. 



[ No spicules present in test 5 



p. /With an atrial siphon Distoma. 



I With a trifid atrial langue t Heterotrema. 



Colella, Rerdman, 1885 * (MS., 1880). 



Colony more or less club-shaped, composed of a peduncle 

 attached at the base, and bearing on its summit a more or less 

 ellipsoidal ascidiariura. 



Ascidiozooids imbedded in a common test ; usually arranged in 

 lines but not divided into systems. ISTo common cloacal cavities. 

 Body composed of thorax and abdomen, and a long ectodermal 

 vascular process from the posterior end of the latter. Aper- 

 tures six-lobed, not prominent. 



* This genus was fully diagnosed, with Colella Thomsoni as the type species, 

 in my thesis for the degree of Doctor of Science, sent in to the University of 

 Edinburgh and accepted by the Science Degrees Committee in March 1880 ; and 

 was published without material change in the second part of my ' Challenger ' 

 Report, printed off in 1885. 



