540 Mr. W. S. MacrEavs Anatomical Observations 
The genus Boltenia evidently enjoys some degree of locomo- 
tion when its flexible pedicle is agitated to and fro by the waves; 
and it is not improbable that some points of its construction 
render this oscillation necessary to its comfortable existence : 
for we may observe, that one of those Ascidide which come the 
nearest to it in structure (the Cynthia momus of Savigny) does not 
attach itself to rocks, but makes shift to float about in the Gulf 
of Suez by attaching itself to fuci and other submarine plants. . 
oom o 
Tur second animal which I have to illustrate is sufficiently 
distinct from the former to allow me to form a new 
Subgenus. CYSTINGIA. 
ExTERNAL CHARACTER. Body with a sub-coriaceous test, 
.. affixed by the summit to a very short pedicle, which is 
in the same line with the two orifices. The branchial 
orifice quadrifid and lateral, the anal irregular and ter- 
minal; both being so little prominent as not to alter the 
form of the body. 
AÁNATOMICAL CHARACTER. Branchial pouch membranaceous, 
indistinctly reticulated, and divided into longitudinal 
folds. The tentacula of the branchial orifice compo- 
site. Intestinal canal lateral. Stomach very large, ex- 
tending almost the whole length of the body. Ovaries 
two, composed of globular ova disposed in free racemes 
on each side of the body, with the branchial pouch and 
stomach between them. 
This genus comes nearer to Boltenia than to any other hitherto 
described ; and they may prove eventually to be only two sub- 
genera, 
