204 



THE SILVER SHELL. 



Thracia airta^ Conr. , Thra'-shi-a cur'-ta. In form 



and 



markings 



but it is 



its shell resembles Fig. 151, 

 somewhat oblong and wrinkled at the rear end of the 

 valves. Ligament external, hinge-teeth small, pallial 

 sinus shallow, length from an inch to two inches. 

 Periplo77ia ar^gentaria^ Conr., Per-i-plo'-ma ar-gen- 

 This is a pretty species, easily rec- 

 ognized by its peculiar 

 spoon-like hinge-teeth. Ob- 

 long, beaks near the posterior 

 end, pallial sinus small, right 

 valve bulged, left one flat- 

 tened. White, smooth, with 

 fine lines of growth, silvery 

 within. Length an inch or two; southern. 



Cor'-bu-la lu-te'-o-la. Shell 



a small Donax, yellowish, 



Ligament internal, in 



\^alves rather thick, 



at one corner. The 



is onlv 



Cdrbula hiteola^ Cpr. 

 shaped somewhat like 

 marked with lines of growth, 

 a small pit; pallial sinus small, 

 incurved at the edges, angled 

 length of this southern species 

 of an inch. 



three-eighths 



