158 DIMYARIA. 



** Shells Mith an internal ligament, and not gaping at the sides. 



Genus 51 ERYCINA. — Lamarck. 



Generic Character. — Transverse, subinequilateral, equi- 

 valve, rarely gaping ; with two primary teeth, unequal, di- 

 verging, with a pit interposed; lateral teeth two, oblong, 

 compressed, short, and inserted ; ligament internal, situated 

 in a pit. 



There is much difficulty in judging of the hinges of this genus, owing 

 to theu' equivocal character. 



Eiyclna striata. — The Striated Erycina. Plate 

 XVII. fig. 21. Yellowish-green, with strong transvei^e 

 striae. One inch long. Inhabits the Indian ocean. 



Ge7ius 52 CRASSATELLA. 



Generic Character Inequilateral, suborbicular, or trans- 

 verse, close; primary teeth two, somewhat divergent, with 

 a hollow at the side ; lateral teeth, none or obsolete ; liga- 

 ment internal, inserted into a pit in the hhige. 



There is a close affinity- bet\\ixt this geniis and Mactra and Lutraria ; 

 like them it has the ligament internal, and attached to the primary 

 canities of each valve, but when closed, the sheUs fit exactly, and do 

 not gape like these genera. The Ugament in some of the species is 

 pai"tially external, but less visible than in the genus Amijhidesma. 



Crassatella Kingicola. — The King's Island Crassa- 

 TELLA. Plate XVIII. tig. 1. Ovate, orbicular, yellowish- 

 white, with obsolete rays ; very minutely striated trans- 

 versely; the umbones somewhat plicated. Two inches long. 

 Inhabits the sea at King's Island, New Holland. 



Genus 53.— LIGULA Montagu. 



Ger^eric Character. — Equivalve, with a broad transverse 

 tooth in each valve, projecting inwards, furnished with a 

 pit for the reception of the cartilage, and in some species a 

 minute tooth. 



