76 ISCHNOCH1TON. 



The prominent specific characters are the coloration, which is much 

 like typical Mopalia lignosa Gld., and the apparently smooth surface, 

 seen under a lens to be very densely, evenly granulated throughout, 

 and having fine, low, subobsolete riblets on the lateral areas and end 

 valves. These riblets are hardly visible unless viewed under a cross 

 light with a good lens 



I. SCABRICOSTATUS Cpr. PI. 16, figs. 55, 56. 



Shell oval-oblong, rather elevated, the dorsal ridge strongly car- 

 inated ; side-slopes slightly convex. Orange colored, with a few 

 darker spots along the riblets of the lateral areas and the posterior 

 margin of each valve. 



Median valves slightly and obtusely beaked (when not eroded), 

 having slightly raised lateral areas, which are weakly, almost obsoletely 

 tricostate, and bear a few inconspicuous low nodules, more numerous 

 on the posterior riblet ; the entire lateral areas being covered with 

 a granulation similar to that of the central areas. Central areas 

 closely and minutely scaly -granulose in the middle, ribbed at the sides, 

 the granulation extending over the riblets, crenulatiug them and 

 causing the interstices to appear pitted. 



Anterior valve granulated, and having many (about 24) delicate 

 riblets, which are obsoletely pustulose. Posterior valve smaller than 

 the anterior, having the mucro slightly in front of the middle, sculp- 

 tured like the head-valve, but with less distinct radii. 



Interior flesh colored. Anterior valve with 10, median valves 1-1 

 slits. Sinus wide, squared. 



Girdle orange colored, densely covered with very minute, unusu- 

 ally wide and short, striated scales, each measuring about one-ninth of 

 a mill, in width. 



Length about 7, breadth about 4J mill.; divergence 95. 



Catalina Island, California. 



Carpenter's description, given on p. 121 of vol. xiv, is misleading 

 in the account of the sculpture. It has no " rows of prominent gran- 

 ules." The entire surface is shagreened, the second valve (drawn in 

 figure 56) has several short radiating riblets in the front of the 

 dorsal tract ; the other valves have longitudinal riblets developed on 

 the pleura only. The scale-like granulation of this species is 

 coarse, when we consider the size of the shell, but the girdle scales 

 are unusually small, very short and broad. 



But one specimen is known to have been found, this being no. 

 16268 of the Smiths. Inst. Coll. 



