on the Natural Group of Tunicata. 541 
genera, of which we want the intervening links to enable us to 
form an accurate notion of the genus to which they belong: At 
present, however, the characters, both internal and external, of 
the animal which I am about to describe, are so different from 
those given as generic by Savigny to Boltenia, that it is impos- 
sible to assign it to this group, which indeed has nothing in com- 
mon with it, but externally a pedicle, and internally composite 
tentacula. 
Pallas has in the Nova Acta Petropolitana described under the 
name of Ascidia globularis a species of this family, which he 
found during his Siberian journey plentiful on the shallow sandy 
shores of the Arctic Ocean ; and as his description is very vague, 
and principally differs from that of the species before me in re- 
spect to size and the position of the apertures, it is just possible 
that the same animal may be intended; a circumstance which 
would be rather interesting in a geographical point of view. He 
describes it as being of the size of a large cherry, and fixed by 
a very short peduncle to the fine sand of those shores, the par- 
ticles of which being agglutinated to its surface, make it appear 
rough. 
If, however, both the apertures of the animal described by 
Pallas be truly terminal, and the peduncle be placed as repre- 
sented in his figure, it is not only a different species from the 
following, but probably a very different genus. 
CysTiNGIA GRIFFITHSII. 
C. ovato-globosa cineracea glabra semipellucida, pedunculo vix 
. longitudine corporis. 
ps Tas. XIX. 
Descr. Envelope semipellucid, yellowish. Mantle very thin, and 
provided near the branchial and anal orifices with a reticula- 
tion of circular muscles nearly at right angles to each other. 
4a 2 Tentacula 
