DIMYARIA. 149 



subinequilateral, close ; binge with two strong, diverging, 

 primary teeth in the right valve, and two very unequal teeth 

 in the other; ligament external, on the longest side. 



Distinguished from Crassatella, by the position of the ligament ; ami 

 from Vonlis, by liaving but two teeth in eacli valve ; one of wliich is, 

 besides, but slightly projecting. 



Astarte Scotica. — The Scottish Astarte. Plate 

 XVII. fig. 3. Somewhat heart-shaped, a little compressed, 

 with regular parallel grooves and ribs; impressions under 

 the beak lanceolate ; covered with a yellow-brown epider- 

 mis ; inside pure white ; margin broad and plain. One inch 

 long. Inhabits the Scottish and Devonshire coasts. 



Genus 31. — CAPSA. — Lamarck. 



Generic Character. — Transverse, equivalve, valves ap- 

 proximate and close; hinge with three primary teeth in the 

 right valve, and a single bifid tooth in the left, inserted into 

 a cavity in the opposite one ; no lateral teeth ; ligament 

 external. 

 The ligament is on the short side, as in the genus Donax. 



Capsa laevigata. — The Polished Capsa. Plate XVII. 

 fig. 4. Triangular, subequilateral, obsoletely striated trans- 

 versely; covered with a greenish-yellow epidermis; inside 

 violet towards the umbones. Two inches long. Inhabits 

 the Indian ocean. 



h Shells with one or two lateral teeth. 



Genus 32. — DONAX. — LitmcBu^. 



Generic Character. — Transverse, equivalve, inequilateral; 

 with the anterior side very short and obtuse ; two primary 

 teeth in one or both valves; and one or two lateral teeth, 

 more or less apart; ligament external, short, inserted at the 

 posterior impression. 



A well marked characteristic of tliis genus is, its having at the hinge, 

 besides the primary teeth, one or two lateral teeth, some^vhat distant, 



N 3 



