( 12 ) 



DIVISION VII. CARDIACEJE, 



GENERA. 



on 

 toge- 



4. Cardium. Lin. 



Equivalved, sub*cordi~ 

 form, beaks protuberant, 

 valves dentated or folded 

 on their internal edge ; 

 longitudinal ribs, often ponding teeth : 2 lateral 

 thorny or scaly. Fig. 38. teeth, wide apart. 



4 cardinal teeth 

 each valve, close 

 ther, oblique, joining in 

 a cross with the con es- 



Ligament exterior, 

 very short : muscular 

 impressions not very ap- 

 parent. (1) 



No peculiar angle on the beaks; the anterior side at least as large as the 

 posterior. 



/?. Beaks keeled or with an angle; the posterior side often larger than the 

 anterior. 



2. Isocardia. Lam. M. 



Equivalved, cordiform, 

 ventricose ; beaks wide 

 apart, diverging, rolled 

 in a spire. Fig. 39. 



2 flattened cardinal 

 teeth, one of which 

 curves and enters under 

 the beak : 1 elongated 

 lateral tooth . 



Ligament exterior, 

 forked on one side. 



3. Hiatella. Baud. M. 



Equivalved, very ine- 1 small cardinal tooth 

 quilateral, gaping at the on the right valve, and 2 

 upper edge. Fig; 40. oblique teeth a little 



larger on the left valve. 



4. Cypricardia. Lam. M. 



Equivalved, inequilate- 3 cardinal teeth under 

 ral, obliquely elongated, the beaks : 1 lateral 

 Fig. 42. ' tooth. 



(1) They are found in all seas. Amongst the fossil Gardia of Europe, species 

 may be recognized which now live in the Asiatic Ocean. They bury themselves 

 in the sands of the coasts. Foss. in London Clay, Crag Marl, Woolwich Loam and 

 Green Sand, Limestone Roc*k, Derbyshire Peak Rock, at Grignon, Bourdeaux, Plai- 

 sance, Touraine, Sienna, St. Jean d' Asse, Chauffour, Ban, Paris, Pontchartrain^ 

 Mont for l-Lomori, Cherbourg. The fossil species Cardium Hibcrnicum, is so sin- 

 gular in form, that notwithstanding its affinity to the Cardia in other respects,. 

 M. Lamarck thinks, were its hinge known, it would form a distinct genus. 



(2) This shell is generally found amongst the fucus in the sand of the Northern 

 Seas. 



(3) New-Holland, Coast of Guinea, St. Domingo. Foss, Italy, Caen, Moutiers* 



Ligament exterior. (2) 



r 



Ligament exterior . (3) 



