154 DIMYARIA. 



TRIBE II. LITHOrnAGI. 



Shells which bore into clay and other substances, with 

 accessory plaits, and more or less gaping at their anterior 

 side ; ligament external. 



Genus 42.— YE'NERJJPIS.— Lamarck. 



Generic Character Transverse, inequilateral; posterior 



side short, the anterior slightly gaping ; hinge with two 

 primary teeth in the right valve, three in the left, sometimes 

 with three in each ; teeth small, approximated, i>araliel, and 

 slightly divergent ; ligament external. 



Nearly allied to Venus, but the teeth are differently disposed, having 

 tliree piimai*y teeth in one of the valves at least. Some of the species 

 of tliis genus, together -vAith certain oval Sfjecies of Yenus, constitute 

 the genus Pullastra of Sowei'by. 



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. Inhabits the. British seas, boring into rocks and 

 clay. 

 It does not appear to be distinct from Venus Pullastra. 



Genus 43— PETRICOLA. —Zawiarc.^. 



Generic Character. — Subtrigonal, transverse, inequilater- 

 al; posterior side rounded, anterior attenuated, and slightly 

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

 only. 



Petricola pholadiformis. — The Pholas-SHAPED Petri- 

 coLA. Plate XVII. fig. 17- Transversely elongated; um- 

 bones very small; with transverse, rough, prickly stri;e; 

 posterior side extremely short. Three inches long. In- 

 habits the Australian seas, boring into wood and rocks. 



