DIMYAIRA. 131 



inequilateral, close ; hinge with two strong, diverging, primary 

 teeth in the right valve, and two unequal ones on the other ; 

 ligament external, broader than long. 



Distinguished from the crassatella, 'oy the position of the lig-ament ; and 

 from Venus in having but two teeth in each valve ; one of which is, besides, 

 but slightly projecting. 



Crassina Scotica.— The Scottish Crassina. Plate XVI J. 

 %. 3. Somewhat heart-shaped, a little compressed, with regu- 

 lar parallel grooves and ribs ; impressions under the beak lan- 

 ceolate ; covered with a yellow-brown epidermis ; inside pure 

 white ; margin broad and plain. One inch long. Inhabits the 

 Scottish and Devonshire coasts. 



Genus 3\.—C AFS A.— Lamarck. 



Generic Character. — Transverse, equivalve, valves approxi- 

 mate and close ; with three primary teeth in the right valve^ and 

 a single bifid tooth in the left, inserted into a cavity in the op- 

 posite one ; destitute of 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 vio- 

 let towards the umbones. Two inches long. Inhabits the 

 Indian ocean. 



** Shells vvith one or two lateral teeth. 



Genus 32.— DONAX.— iinw«7«. 



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 this genus is, its having at the hinge be- 

 sides the primary teeth, one or two lateral teeth, somewhat distant, and se- 

 parated from the cardinal teeth, similar to those of the Mactra, Lusinse, and 

 Tellinse. In the genera Cytherea and Venus, the siiortest side of the shell is 

 always the posterior, and the longest and largest, having the ligament at- 



