220 MOLLUSCA FROM THE CRAG. 



Shell transverse, wedge-shaped, and smooth, inequilateral ; posterior side very short 

 and truncated ; ventral margin nearly straight and crenulated. 



Length, 1 inch. Height, \ an inch. 



Locality. Red Crag, Sutton. Recent, Mediterranean. 



This shell is rare in my cabinet, and I have met with it from one locality only. It 

 appears to differ from the preceding, and to correspond with the Mediterranean form in 

 having a much shorter posterior side, it is also smoother externally, with less distinct 

 radiating striae, and the ventral margin not so much curved ; the dentition is much the 

 same in both species, though somewhat more strongly marked in D. anatinus* The 

 sinus in the mantle mark extends nearly to the middle, rather further beyond the 

 hinge than in the British shell, with a few other minor differences ; and as the British 

 Conchologists have separated the recent shells into two species, the fossil forms seem 

 to warrant a similar proceeding. Philippi mentions this among the Red Sea Shells 

 collected by Von Hemprich and Ehrenberg. 



3. DONAX POLITUS, Poli. Tab. XXII, fig. 9, a, b. 



TELLINA POLITA. Poli. Test. Sicil., vol. i, p. 44, pi. 21, fig. 14, 1791. 



VINACEA. Gmel. Syst. Nat., p. 3238. 



DONAX COMPLANATA. Mont. Test. Brit., p. 106, pi. 5, fig. 4, 1803. 

 Phil. En. Moll. Sic., vol. ii, p. 28, 1844. 



LONGA. " Bronn." Phil. En. Moll. Sic., vol. i, p. 37, pi. 3, fig. 13, 1836. 



GLABRA. S. Wood. Catalogue, 1840. 



POLITUS. Forb. and Hani. Hist. Brit. Moll,, vol. i, p. 336, pi. 21, fig. 7, 1848. 

 CAPSA COMPLANATA. G. B. Sow. Gen. of Shells, No. 10, fig. 2. 



PSAMMOBIA POLITA. Costa. Catal. Test. Sicil., p. 20, No. 14. 



Spec. Char. Testa elongato-cuneiformi, complanatd, l&vigatd, politd, tenui, inaqui- 

 laterali ; later e antico longiore ; latere postico angulato ; margine mtegro. 



Shell elongately wedge-shaped, flattened or compressed, smooth and glossy, thin, 

 inequilateral ; anterior side the longer, produced ; posterior angulated ; margin 

 smooth. 



Length, 1 inch. Height, \ an inch. 



Locality. Cor. Crag, Sutton and Gedgrave. 



Recent, Britain and Mediterranean. 



Small specimens not exceeding half an inch in length are abundant at Sutton, but 

 fragments indicate a magnitude of at least an inch and a quarter. This elegant shell 

 is beautifully glossy in those specimens that are well preserved, but the generality are 



* In the ' Hist. Brit. Moll.,' vol. i, p. 340, the hinge of D. trunculusis said to be destitute of lateral teeth, 

 while they are described (p. 332) as being present in D. anatinus. I have not been able to make that distinc- 

 tion. There is a prominent lateral tooth in my fossil on the posterior side, beyond the ligamental support. 



