26 CONCHYLIA— l>/r/fF«^. 6. 



Shell transverse, equivalve, inequilateral, open at the anterior 

 end. Hinge with two teeth in one valve closing between three 

 in the other : lateral teeth none. Ligament external. 



The individuals of this family, like most of the inhabitants of 

 rocks, are exceedingly variable in their figure and outline. In 

 the structure of the teeth they much resemble the genus Venus ; 

 but we believe that there are uniformly only two in one of the 

 valves, with sometimes the obscure rudiment of a third, and three 

 in the other : the gape also, or opening at the anterior end, 

 materially distinguishes them. With the Donax tribe they hare 

 no relative connexion. They are imbedded in rocks, or found 

 wedged in the interstices. 



iius. Petricola testa polymorphd, lamellis transversis reflexis, 

 interstitiis longiludinaliter striatis. 

 Shell variously shaped, with transverse reflected plates, the 

 interstices of which are striate longitudinally. 

 Tab. nost. 2, fig. 14. 

 Donax Irus. Linn. Syst. Nat. p. 1128. 



Gtnelin, Syst. p. 3265. 

 T?<r<o», Linn. Syst. i v. p. 216. 

 Pennant, Brit. Zool, iv. p. 200. 

 Chemnitz, vi. p. 271, tab. 26, fig. 268 to 270. 

 Montagu, Test. Brit. p. 108 and 573. 

 Donovan, Brit. Shells, i. tab. 29, fig. 2. 

 Linn. Trans, viii. p. 77. 

 Turton, British Fauna, p. 156. 

 Dorset Catal, p. 84, tab. 12, fig. 6, left hand. 



