136 CIMYAIRA. 



Nearly allied to the Venus, but the teeth are differently disposed, havini? 

 three primary teeth in one of the valves, at least. 



Venerupis perforans.— The Perforating Venerupis. Plate 

 XVII. fig. 16. Sub-rhombic, transversely striated, wrinkled 

 on the anterior side; brown, with a white inside, sometimes 

 with a tinge of purple. Three quarters of an inch broad. In- 

 habits the British seas, boring into rocks and clay. 



Genus 43.— PETRICOLA.— Zawarc^. 



Generic Character. — Subtrigonal, transverse, inequilateral; 

 posterior side rounded, and the anterior attenuated, and slightly 

 gaping ; hinge with two teeth in each valve, or in one valve 

 only. 



Petricola pholadiformis.— The Phol as- Shaped Petricola. 

 Plate XVII. fig. 17. Transversely elongated ; umbones very 

 small ; with transverse, rough, prickly striae ; posterior side ex- 

 tremely short. Three inches long. Inhabits the Australian 

 seas, boring into wood and rocks. 



Genus U.—SAXICAV A.— Lamarck. 



Generic C/icmc^er.— Inequilateral, obtuse, and transverse ; the 

 anterior upper margin gaping ; hinge nearly without teeth ; 

 ligament external. 



Saxicava prcEcisa.— The Abbreviated Saxicava. Plate 

 XVII. fig. 18. Oblong, wrinkled, one valve larger than the 

 other, truncated at the posterior end ; of a pale horn-colour. 

 Three quarters of an inch broad. Inhabits the British seas, in 

 cavities bored in rocks, stones, and wood. 



TRIBE III. CORBULACEA. 



Inequivalve shells, with an interior ligament ; one of the 

 beaks always projecting beyond the other. 



Genus 4.5 PANDORA.— ZawiorcA-. 



Generic Character. — Shell regular, inequivalve, inequilateral, 



