420 UNDESCRIBED FOHM OF GASTEROPOD MOLLUSK. 



X.— ON AN UNDESCEIBED FOEM OF GASTEEOPOD 

 MOLLUSK FEOM THE EIETH OF FOETH.* 



After the severe storm which occurred in February 1855, two 

 of my pupils, Messrs. Cleland and Bryden, applied to me for 

 assistance in determining a number of animals which they 

 had picked up on the beach opposite the Black Eocks at 

 Leith. The collection, with one exception, consisted of or- 

 dinary forms. The peculiar specimen was a Gasteropod 

 Mollusk, dead, apparently bleached, somewhat rubbed, and 

 presenting the appearance of an Eolis deprived of its plumes. 

 The novelty of its form was, however, specially evinced by 

 the remarkable characters of its branchias, which consisted 

 of a number of closely-arranged longitudinal lamina?, depend- 

 ing from the roofs of true crypts, situated one on each side of 

 the body near the head, and opening out in the lateral grooves 

 under the margins of the mantle. 



The specimen was at once handed over to me, and on 

 examination proved to be a new form closely allied to Di- 

 phyllidia. 



The animal is white, inclining to pale citron, except the 

 branchiae, which are light brownish yellow. 



The body is elongated, ovate, gradually acuminated pos- 

 teriorly, and somewhat depressed. Its extreme length is 1^ 

 inch ; its greatest breadth across the mantle f-inch. 



The mantle is kite-shaped, its posterior angle reaching the 



* This paper was written in the year 1855, and intended to lie read before 

 the Wernerian Society, which it was at that time proposed to reconstitute, but 

 a=, this idea was not carried out the paper was never published. — Eds. 



