324 TELLINID^. 



moderately convex, and almost smooth, and the shell is a 

 little open at either extremity. The lovA'er margin is simply 

 arcuated, with the arch a little flattened near the middle ; 

 both the npper edges are almost straight, and profoundly 

 and almost equally sloping. The sides are very nearly 

 alike in size, the front one is rounded below, and obtuse 

 above, the hinder is bluntly angulated. The beaks are 

 small, but acute and prominent, and are directly inflected, 

 not turning towards either side. The ligament is very minute, 

 and lies at the bottom of the narrow escutcheon formed by 

 the compression of the hinder dorsal margin. There is also 

 a similar though less evident compression in front, whence 

 originates a false or incipient lunule. No umbonal ridge 

 is present. The hinge is only furnished in the left valve 

 with a single denticle ; the right valve has two denticles, 

 and two lateral laminae, of which the hinder is large and 

 more remote, and the front more approximate and decidedly 

 smaller. The cartilage pit is large, much curved, and not 

 at all angular. The length is not quite three-eighths of an 

 inch, and the breadth is about one-sixth less. 



Notwithstanding that it is locally abundant, this cannot 

 be considered a very common species, being found in but 

 very few localities. Perhaps a few miles beyond Portland 

 bridge in Dorsetshire (S. H.), where the high water-mark 

 is indicated upon the muddy surface by the copiously scat- 

 tered shells of this and other Mollusks, may be regarded 

 as its most prolific site. It has occasionally been taken 

 in Northumberland (Alder); at Ramsgate ( Sowerby, 

 M'Andrew); at Portsea and Southampton (Jeftreys); Tor- 

 bay (Alder) ; and met with, though rarely, at Scarborough 

 (Bean) ; and Littlehampton in Sussex (Strickland). 



Mr. Thompson has received some individuals from Larne 

 Lough in Antrim (Ann. N. H. vol. xiii. p. 433), the only 



