5l8 DESCRIPTION OF THE MUSEUM. 



inhabit the seas of hot countries : they are not 

 very common, and are remarkable for their form 

 and colour. The isocardice are very singular shells 

 in the form of a heart, the extremities of which 

 are pointed and twisted like ram's horns. The 

 is., cor inhabits the Mediterranean ; another, the 

 is. moltkiana, a very rare species, was brought 

 by M. Dussumier, from the Chinese seas ; a third, 

 the is. semi-sulcata, comes from New Holland : 

 and a fourth, the is. arietina, is found in a fos- 

 sil state in Italy, whence it was brought by 

 M. Cuvier. 



The four genera, cucullcea, area, pectunculus 

 and nucula, compose the family of the arcacece. 

 There are only two species of the genus cucullcea 

 known. The c. auriculifera, which is recent and 

 rare, inhabits the Indian seas: the other, found 

 in the fossil state near Beauvais, was presented by 

 M. Lucas, jun r . W"e have twenty-nine species of 

 the genus area; we shall point out as among 

 the rarest the arc. semi-torta, the ovata and the 

 tortuosa. The shells which belong to the genus 

 nucula are very small and brilliant: we have 

 seven species, one of which, the area nucleus., 

 Lin., is common on the coasts of France. 



Next to the arcacece are. the trigonice; to which 

 belongs the trig, pectinata, a very valuable shell, 

 from its rarity, and its being the only recent spe- 



