A. E. Verrill — Study of the family Pectinidm. 75 



oi" serrations. On the inner surface there are radial grooves corre- 

 sponding to the external ribs. The hinge-margin is thin, with a 

 slender submarginal ligamentary groove and a small triangular 

 resilial pit in the center. The color is variable. The single valve 

 from station 2571 is uniform lemon-color ; those from the other 

 locality are chestnut-brown and reddish, variegated with paler, and 

 sometimes with white blotches. 



Length of largest specimen, 5 5™'" ; height, 6™"' ; length of dorsal 

 margin, 4™"\ 



Off Martha's Vineyard, in ]356 fath., dead ; West Indies, in 25 to 

 72 fath., living. 



This species is allied to C. varia of Europe, but when compared 

 with the young of that species, of the same size, the radial ribs are 

 found to be fewer and coarser, and there are other differences which 

 render it probable that they are distinct species. The ribs are 

 stronger and fewer than in C. Islandica, and the auricles are differ- 

 ent in shape. It is probable, however, that it grows to a much 

 larger size than any of the specimens obtained. It may possibly 

 prove to be the young of some known West Indian species, but does 

 not agree with any known to us. 



Chlamys costellata Verrill and Bush, sp, nov.^ 



Shell small, thin, translucent bluish white, covered on both sides 

 with continuous, elevated, and somewhat thickened, well separated 

 radiating riblets, of which there are more than thirty on our largest 

 example. Length of the shell considerably less than the height. 

 Dorsal hinge-margin elongated, especially on the anterior end. In 

 the right valve the anterior auricle is considerably elongated, 

 obtuselj' rounded or subtruncate at the end, with a wide, angular 

 byssal notch beneath it, and a broad, smooth, angular area next to 

 the body of the shell, above which there are three well marked, 

 angular, radial ridges, separated by wider concave interspaces. 

 Posterior auricle small, triangular, the outer end convex, forming a 

 little more than a right angle and with the posterior margin nearly 

 straight and without any distinct notch. 



The dorsal margins of the body of the shell are nearly straight 

 and diverge at less than a right angle. The ventral margin is pretty 

 evenly rounded, but a little produced in the middle. The beak is 



' Figured iu an unpublished paper sent to Proc. U. S. Nat. Mas. several months 

 ago. 



