438 TAPESINiE. 



slightly diverging; ligament external. Muscular impres- 

 sions large, ovato-semilunar ; pallial impression posteriorly 

 sinuated ; sinus wide, rather deep, sub- trigonal, horizontal. 



Sy?i. Irus, Oken. Venerupis, Lamarck. 



Ex, K. Irus, Linnams, pi. 109, fig. 4. Shell, R. Irus, 

 fig. 4, a, 4, b. 



The foot in this genus is smaller than in Tapes, and 

 the siphons are united as far as their ends, which distin- 

 guishes the animal from that of Petricola. The species 

 are most numerous in Northern and temperate climates, 

 heing found in Europe, the British Islands, Behring's 

 Straits, Kamtschatka, the Crimea, Tasmania, and the 

 Canary Islands ; they inhabit the holes and crevices of 

 rocks, in which they are usually fixed by the byssus. 



Species of FaipeUaria. 



brevis, Qiioy and Gaim. foliacea, Desk. 



carditoides, Lam. interjecta, Desk. 



Cordieri, Desk. Irus, Linn. 



corrugata, Desk. oblonga, Sow. 



crenata, Lam. rnacropbylla, Desk. 



Diemenensis, Quoy and monstrosa, Chem. 



Gaim. solida, Sow. 



distans, Lam. subclecussata, Desk. 



elliptica, Soiv. tenuistriata, Jonas. 



exotica, Lam. texta, Desk. 



Genus TRAPEZIUM, Megerle von Muhlfeldt. 



Shell equivalve, inequilateral, obliquely or transversely 

 elongated, the posterior side very short. Hinge with three 

 cardinal teeth, placed beneath the beaks, in each valve, with 

 a simple, rather elongated, lateral tooth extending along 



