316 Miscellaneous. 
Obs. The Shetland Nudibranchs and Cephalopods have not 
been sufficiently investigated. Lovén’s ‘ Index’ and a further 
list of Swedish Nudibranchs which he lately sent me contain 
60 species of that order, out of which 22 only have been iden- 
tified as Zetlandic. He also gives 9 species of Cephalopods, 
of which 3 only are Zetlandic. The southern distribution of 
our Nudibranchs is very little known. or the preparation of 
the present list of Nudibranchs [ am in a great measure in- 
debted to the late Mr. Alder and to Mr. Norman. Forty-five 
oe of mollusca (marked +) have been discovered in the 
hetland seas since the publication of Forbes & Hanley’s 
‘History of British Mollusca and their Shells.’ 
MISCELLANEOUS. 
On a new Class of Echinodermata. 
By C. Semper. 
M. Semper has made an anatomical investigation of the genus 
Rhopalodina of Gray, which has led him to rather remarkable re- 
sults. The animal had been classed by Dr. Gray, because of the 
form of its body, among the Holothurie. This body is formed of an 
anterior part having the form of a cylindrical peduncle, and of a 
spherical posterior part or abdomen. In this hinder region, at the 
point opposed to the insertion of the peduncle, are seen ten ambu- 
lacra, to which correspond in the interior, as in the Holothurie, ten 
radiating muscles, ten aquiferous canals with their ampulle, and 
ten nerves. These ten rays of the abdomen, moreover, are prolonged 
into the peduncle, but without bearing any feet. 
At the free extremity of the peduncle are the mouth and the 
anus, side by side. The margin of the mouth is entire; that of the 
anus is formed by a circle of ten papillae. The tentacular crown of 
the pharynx is formed of ten pennated tentacles, which, in the two 
individuals studied by M. Semper, were hidden in the buccal cavity. 
The pharynx and the terminal part of the intestine consequently 
pass side by side in the interior of the peduncle. At the point where 
the peduncle enlarges to form the spherical abdomen, the anal intes- 
tine bears four long ceca, like the lungs of the Holothurie. At the 
corresponding point of the pharynx, between that organ and the in- 
testine; appears a little swelling, serving as the point of attachment 
of a crowd of little blind tubes. These are the generative organs, 
_ constructed on the type of those of the Holothurie. The stomach 
forms in the abdomen a spiral with numerous turns and a double 
loop. 
Of the ten rays above mentioned, five correspond with the pha- 
rynx and five with the intestine. The five radial muscles of the 
pharynx are attached, as in the Holothuriz, to five radial pieces of 
the calcareous pharyngeal ring, which is formed of ten pieces in all. 
In this place there ought to exist a circular aquiferous vessel, as 
follows from the existence of two vesicles of Poli, Round the anus, 
