202 MOLLUSCA. 
ed by a cylindrical rib from the pylorus to the anus. Liver 
absent or indistinct. 
Genus StTyELA.—Ovarium divided, one division at least 
on each side. S. Canopus. Sav. tab. viii. f. 1. 
Genus Panpocra.—Ovarium single, and situate in the 
told of the intestine. The Ascidia conchilega, a native 
species is the type. 
2. Apertures with indistinct rays, or more than four. 
The external tunic is here soft, easily cut, and translu- 
cent. The rays (when existing) of the branchial orifice 
amount to eight or nine; and those of the anal to six at 
least. The branchiz are destitute of longitudinal folds. 
The tentacular filaments of the branchial circle are simple. 
Liver indistinct. Ovarium single. 
a. Body pedunculated. 
The stalk is here placed at the base, and serves to sup- 
port the body, being of an opposite character from that of 
the Boltenia. 
Genus CLavetrna.—Branchial and anal orifices with- 
out rays. Angles of the branchial meshes simple. — Intes- 
tine destitute of arib. The Ascidia clavata of Pallas, and 
the A. lepadiformis of Miiller belong to this genus; the 
latter ofthese is now recorded as a British species. 
is As connected with this group the small Ascidia, figured 
and described by Mr. Lister in the Philosophical Transac- 
tions for 1834, deserves particular notice, as the following 
important observations which he has recorded, sufficiently 
indicate. They will indeed be perused with peculiar inter- 
est by all who are practically engaged in the study of mol- 
Juscous animals. 
This compound animal occurs in groups that consist of 
