15G DBIYARIA. 



Although having some affinity to the genera Crassatella, and Ungu- 

 lina, they are at once distinguished by the inequality of their valves, 

 and the strong primary elevated tooth. 



Coihula Nucleus The Kernel Corbula. Plate XVII. 



fig. 20. Somewhat triangular, strong, with the under valve 

 much larger than the upper one; transversely striated; 

 covered with a thick, brown epidermis. Half an inch long. 

 Inhabits the British seas. 



TRIBE IV. MACTRACEA. 



Equivalve shells, frequently gaping at the lateral ex- 

 tremities ; with an internal or partly external ligament, and 

 the animal having a small compressed foot. 



* Ligament seen externally or double. 



Gent/s 47.— AMPHIDESM A.— Za/«arcA. 



Generic Character. — Inequilateral, transverse, suboval, or 

 somewhat rounded; with sides slightly gaping ; hinge with 

 one or two cardinal teeth, and a narrow groove for the inter- 

 nal ligament; ligament double, the external short, the inter- 

 nal fixed in the internal grooves. 



These possess a peculiar character which distinguishes them from 

 all other bivalves, namely, the two hgaments. 



Amphidesma reticulata. — The Reticulated Amphi- 

 DESMA. Plate XVII. fig. 24. Suborbicular, sub-diaphanous, 

 compressed, finely reticulated ; yellowish-white. One inch 

 and a quarter long. Inhabits the West Indian seas. 



Genus 48.— SOLEMY A.— Zawarc^i. 



Generic Character. — Inequilateral, equivalve, transversely 

 elongated, obtuse at the extremities, with the epidermis 

 smooth, shining, and projecting beyond the margin ; beaks 

 not prominent and hardly distinct ; a dilated, compressed, 

 somewhat oblique cardinal tooth in each valve, slightly con- 



