146 MOLLUSCA FRO^I THE CRAG. 



are found in the same locality, and I have one specimen from the Red Crag in good 

 preservation, exhibiting the same distinction. The figure by Nyst more strongly resem- 

 bles this species than the last one, so also docs that by Philippi. The latter author states 

 his shell to be living in the Red Sea, thus giving a greater probability to its l)cing 

 different from the one living in the British Seas ; a few specimens of apparently the same 

 species from the Older Tertiaries at Brackleshara are in the Cabinet of Mr. Edwards, 

 one of which has been figured in Mr. Dixon's work above referred to. In comparing 

 them with the Crag specimens some trifling differences may be observed, but they 

 do not appear of sufficient importance for specific distinction, and the Crag shell is in 

 all probability the prolonged existence of the Bracklesham fossil. In dental characters 

 they are precisely the same, but the Crag shell is rather more tumid, and it is also a little 

 longer, the dorsal margin being somewhat less rounded than in the older shell, and the 

 exteriors of the Crag specimens have merely fine and somewhat irregular lines of growth, 

 while the Bracklesham fossil has rather more regular concentric strise, they however both 

 present sufficient distinction to justify a separation from the recent British species. 



3. DlPLODONTA ? ASTARTEA, Nl/st. Tab. XII, fig. 2, CI, b. 



Tellixa astautea. Nyst. Recli. Coq. Foss. d'Anv., p. 5, pi. 1, fig. 18, 1835. 

 LuciNA GYKATA. S. Wood. Catalogue, 1840. 



— ASTARTEA. Nyst. Coq. Foss. de Belg., p. 121, pi. 6, fig. 4, 1844. 

 Mysia Americana? Conrad. Foss. Shells of the Med. Tert. United States, p. 30, pi. 16, fig. 2. 

 DlPLODONTA PARVULA? Nyst. Coq. Foss. de Belg., p. 139, pi. 7, fig. 2, 1844. 



Sjiec. Char. Testa obltqud, ovato-obiculari, depressitisculd, inosquilaterali ; in senec- 

 tute iniiis spissatd ; postice majiore, antice subangulatd ; dente cardinali hifido. 



Shell oblique, ovately orbicular, somewhat depressed, inequilateral, inside of 

 specimens thickened ; posterior side the larger, anterior subangulatcd : cardinal tooth 

 bifid : no lunule. 



Diameter, fths of an inch. 



Locality. Cor. Crag, Sutton. Red Crag, Sutton. 



This shell is very abundant in the Red Crag, but it is rather scarce at one locality, 

 from the Older Formaiton of the Coralline Crag, and presents some slight differences, 

 though not sufficient to remove it from the species. 



Our shell measures three quarters of an inch from the anterior to the posterior 

 side, and about the same or a trifle less from tlie umbo to the ventral margin, these 

 proportions are occasionally reversed, but there is in general not much variation 

 in this species : it is somewhat oblique, and measures rather more from the dorsal edge 

 or position of the ligament to the opposite margin than in a contrary direction, although, 

 in the young shell, it is the reverse; the umbones are prominent, the hinge has one simple 

 and one bifid tooth in each valve, the surface is marked with somewhat irregular hncs of 

 growth at considerable distances. The interior in the adult shell is much thickened, 



