A. E. Verrill — MoUusca q/ the New England Coast. 437 



Cryptodon plicatUS Verrill, sp. nov. 



Shell not very small, somewhat swollen, and rather thick for the 

 genus ; triangular-cordate in form, with very high and acute beaks, 

 which curve forward but little. The anterior dorsal margin is 

 nearly straight, but a little concave opposite the rather large, 

 depressed lunular area ; the posterior dorsal margin is broadly con- 

 vex and rendered irregular by the strong plications of the margin ; 

 the ventral margin is well-rounded, strongly angulated or lobed by 

 the plications, and a little produced in the middle, in a line with the 

 median ridge. The shell is remarkable for the unusual number of 

 plications and undulations of its surface. Posteriorly there are two 

 very large, much raised, sharply angulated plications, with a very 

 deep concave depression between them, and a deep furroAV between 

 the hindermost and the edge of the shell ; the second and larger 

 fold is separated from a rounded or obtusely angulated median 

 ridge by a broader concave depression. This median ridge is large 

 and very distinct, and somewhat angular ventrally ; farther forward 

 there is a similai", but less mai'ked, ridge, extending to the anterior 

 part of the ventral margin. Anteriorly there is a very large, long- 

 cordate, nearly smooth, concave lunule, which is bounded by two 

 small, distinct posterior ridges, which are near together and run to 

 the antero-ventral angle. The surface is covered by irregular and 

 rather strong lines of growth, which become somewhat lamellose in 

 crossing the strong plications. The hinge-margin is considerably 

 thickened behind the beak, with a deep and conspicuous, curved lig- 

 amental groove, back of which the edge becomes thin and flaring. 

 The interior is angulated, corresponding to the exterior plications, 

 and is marked by irregular radial stride near the ventral margin. 



Length of the largest specimen, 11™'"; height, IS"""'; thickness, 



omm 



The largest and most typical example is a valve from station 2,193^ 

 N. lat. 39° 44' 30", W. long. 70° 10' 30", in 1,122 fathoms (No. 44,825). 

 A young living specimen, apparent identical, was taken at station 

 2,205, in 1,073 fathoms (No. 44,826). 



This species is closely related to C. grancUs V., but it has more 

 numerous and more strongly developed plications; its beaks are 

 more elevated and less curved forward, so that the form is more 

 triangular ; the ventral margin is less produced in the line of the 

 median ridge ; the shell also appears to be thicker and more swollen. 



