MYA. GAPER. 99 



white and somewhat polished : hinge with a projecting 

 hollow tooth in each valve, with a cavity on the curtilage 

 .side : length three-quarters of an inch j breadth au inch 

 and a quarter. 



Western coasts, and Dublin bay. v. v. 



4. Mya pubescens. Rough Gapsr. Fig. 35. 



Mya declivis. Wood.pL 18: f. 2 Dorset Cat. pi. 4. f. 6. 



Shell oblong-oval, thin, semitransparent, yellowish- 

 Vvhite, roughened all over like shagreen, rounded at one 

 end, slightly truncate and angular, and a little gaping at 

 the other, irregularly striate transversely ; one valve deeper 

 and larger than the other, so as in some measure to inclose 

 it ; the front margin often a little contracted near the mid- 

 dle : beaks prominent, incurved, the points not placed quite 

 opposite, but crossing each other, and forming an angular 

 slope down the cartilage edge j inside white, but not glossy : 

 hinge with a strong projecting hollow tooth in each valve, 

 with a deep cavity on the posterior side, the opposite side 

 projecting into a strong rib which runs along the middle 

 of the cartilage edge forming a deep groove ; besides this 

 is another rib which runs rather obliquely from the tooth 

 towards the truncated end : length of the specimen before 

 us two inches and a half \ breadth three and a half j but it 

 is seldom found so large. 



In the belief that these two shells are quite distinct, we 

 are supported by the opinion of some highly respectable 

 conchologists. Although they are sufficiently abundant 

 on the Western coasts, no intermediate size has been yet 

 discovered. One is roughened all over ; the other is quite 

 smooth, except at the cartilage slope. The beaks of M. pu- k 

 bescens cross each other, like the mandibles of the Loxia 

 curvirostra, or Cross-beak : but the most striking and ma- 

 terial difference is the strong rib and groove along the car- 

 tilage edge : there is also some difference in the teeth. 

 For the present, therefore,, we are inclined to offer them as 

 distinct species, suggesting at the same time a close atten- 

 tion to their natural history. 



In the Memoirs of the Wern. Soc. p. 505. pi. 24. f. 4, Mr. 



Brown has described and figured a shell under the name 



qf M. pellucidiij irom the cabinet of Dr. Taylor of Dublin, 



K. 2 which; 



