132 AMERICAN JOURNAL 



Genus FISSURELLID^EA, D'Orb. 

 FlSSURELLIDiEA BIMACULATA, n. S. 



Qlypidella f bimaculata, Dall, MSS. 1866. 



Soft parts. Animal much larger than the shell, which is nearly 

 covered by the mantle. Mantle thick, tough, almost coriaceous, 

 covered with an infinite multitude of fine papillae, closely crowded, 

 giving the surface a velvety appearance. Small round tufts of 

 longer papillae are distributed in an irregular, radiating manner, 

 rather sparsely. Circumference smooth, even ; border around 

 the visible part of the shell, smooth or papillose, differing in 

 different individuals. Color marbled purplish, yellowish or pink ; 

 one or two specimens have a pair of broad, black, parallel streaks 

 running longitudinally along the middle of the back. Mantle 

 entirely covering and hiding the head, tentacles, foot, &c. 



Foot oval, smaller than the circumference of the mantle, edges 

 even, sides a little granular. Overhanging under surface of the 

 mantle smooth. Around the foot between it and the mantle 

 is a single row of papillae, passing from one side of the head 

 clear round the body to the other side, without interruption. 

 Head, eyes, &c. as in Patella. On each side of the head is a 

 round, prominent tubercle, from which a stout filament, as long 

 as a tentacle, extends ; these resemble a pair of accessory ten- 

 tacles. 



Length of animal, 2*7 in. ; width, *9 in. Length of shell of 

 do., *7 in. ; width, -45. 



The color is exceedingly variable. 



It will be seen from the above description that the animal of 

 this species differs strongly from that of Clypidella, to which 

 genus this and another species have been referred by Dr. Car- 

 penter. In Qlypidella, the mantle does not cover the head and 

 foot, and the lateral line of .tubercles does not pass around the 

 latter. The papillae on the edge around the shell are of no dif- 

 ferential value ; and the shell of this species is very nearly 

 covered, while in Qlypidella it is usually more exposed. 



While the present species does not exactly coincide in all its 

 characters with figures of JFissurellidcea, yet it approximates 

 more nearly to that genus than to any other, and I so refer it, 

 provisionally, until further opportunities are afforded of working 

 the subject up more thoroughly. 



Shell ellipsoidal when young, subquadrangulate, and a little 

 narrower in front than behind, when adult. Aperture the same 

 shape as the shell, slightly encroached upon in some specimens 

 by a point on each side. External surface furnished with radi- 

 ating, rounded costae, not bifurcating but widening slightly to- 



