42 



margin; beaks central; hinge callus large, 

 triangular. 



Syn. (Fossil). Thracia pubescens, S. V. Wood in 

 Annals and Mag. Nat. Hist. v. 6.245. Morris, 

 Cat. 102. 



(Recent) tab. DCXXXII. f. 4. Mya declivis. 

 Pennant, Brit, Zool. iv. no. 15. Maton and 

 Racket in Trans. Linn. Soc.v. viii. 36. Wood, 

 Gen. Conch. 93. t. 18./. 2^3. 



Mya pubescens, Pultenei/ in Hutchins's Dorset. 

 27.^.4./ 6. Montague, Test.Brit.40. Turton, 

 Conch. Diet. 99. Brit. Bivalves, 45. pi. 4./. 3. 



Thracia pubescens. Lam. Hist. Nat. 2nd ed. 

 vol. 6. 83. 



In all the essential characters this crag fossil agrees with 

 the recent shell of the western coast of England ; if there 

 be any difference the crag one is smoother and more truly 

 oval, the ventral margin being more curved. 



Both the coralline at Ramsholt and the red crag at Sut- 

 ton furnish this fragile shell ; it is also among the fossil 

 shells of Sicily (Lamarck Hist. Nat. supra), and I have 

 a young individual very closely resembhng it. 



Some doubts having been formerly entertained of the 

 identity of Pennant's shell, which occurs in the Hebrides, 

 with the Dorsetshire species, the name of the latter has 

 been adopted, allhough declivis is the older, and ought in 

 truth to be retained in preference. 



