304 OSTREADjE. 



doubtful natives, rather than entirely excluding a species, 

 the comparative nearness of whose ascertained localities 

 fairly argues the possibility of its being at some time 

 (if not already) discovered as a living inhabitant of our 

 own waters. The following brief description has chiefly 

 been drawn up from Newfoundland specimens. 



Suborbicular or broadly obovate, subequivalve tolerably 

 strong or solid, not transparent, not polished, valves mode- 

 rately convex, the upper one passing from light orange or 

 livid flesh colour to reddish brown, often adorned with 

 about three obscure paler rays, the colouring matter dis- 

 posed in lighter and darker concentric zones ; the lower 

 valve almost white, and decidedly the more shallow. 

 Entire external surface radiated with crowded (from fifty 

 to one hundred) irregularly disposed unequal costellar strire 

 so grouped as to form numerous indistinct and unequal 

 folds, which appear better defined when viewed from the 

 interior. These linear ridges, which exist likewise upon 

 the auricles, where, however, they become coarser, and 

 occasionally less approximate, are roughened, but not 

 aculeated, by an infinite number of minute and peculiarly 

 close- set erect and vaulted scales. Hinge-margin more 

 than equal to half the length of the shell. Auricles well 

 defined : the front one very large, its upper corner nearly 

 rectangular, its costella? few and large upon the lower 

 valve ; hinder auricle moderate in size, only half as 

 long as the front one, but of similar depth ; its angle 

 not very obtuse. Angle of the auricular sinus, which 

 is moderately profound, single, and acute. Internal sur- 

 face white, polished, often a little pearly, sometimes with 

 a subumbonal stain of dull red in the more convex valve ; 

 margin jagged by the external costellre. 



Our largest specimen, which measures four inches in 

 breadth, is not above a third of an inch inferior in its 

 length ; the young shells are much less orbicular, an 

 example an inch long exceeding this measurement in 

 breadth by two-fifths of an inch. 



Although both M tiller and Born are prior in point of 



