316 Miscellaneous. 



Ohs. The Shetland Nudibranchs and Cephalopods have not 

 been sufficiently investigated. Lov^n'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. For the preparation of 

 the present list of Nudibranchs I am in a great measure in- 

 debted to the late Mr. Alder and to Mr. Norman. Forty-five 

 species of moUusca (marked f) have been discovered in the 

 Shetland seas since the publication of Forbes & Hanley's 

 ^ History of British Mollusca and their Shells.' 



MISCELLANEOUS. 



On a new Class of EcTiinodermata. 

 By C. Semper. 



M. Semper has made an anatomical investigation of the genus 

 Mhopalodincc 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 Holothurise. 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 HolothurisB, ten 

 radiating muscles, ten aquiferous canals with their ampullae, 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 caeca, like the lungs of the Holothuriae. At the 

 corresponding point of the pharynx, between that organ and the in- 

 testine, appears a little swelhng, serving as the point of attachment 

 of a crowd of Httle blind tubes. These are the generative organs, 

 constructed on the type of those of the Holothuriae. 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 Holothuria), 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. 



