MOLLUSCA* 8 1 



subnullis." To this genus Lamark brings the Tellina lactea 

 and divaricata of Linnaeus, and the muricata of Chemn. 

 (Conch, vol. xi. p. 209, tab. 199, fig. 1945-6), together with 

 the Venus fimbria ta, and Pcnsylvanica of Linnaeus, and the 

 Jamaicensis of Chemn. (Conch, vol. vii. p. 24, tab. 39, fig. 

 408-9). Cuvier, however, has restored the T. lactea to the 

 genus Loripes, which Poli instituted for its reception. 



7. CARDIUM. This is, perhaps, the best constructed 

 genus which Linnaeus formed. The characters are definite 

 and obvious, and all the species are naturally allied. Hence 

 few changes have taken place in their arrangement. The 

 animal constitutes a new genus in the system of Poli, which 

 he terms cerastis. 



Cuvier is disposed to constitute a new genus under the 

 title HEMICARDIA, for the reception of the C. cardissa of 

 Chemn., commonly called the Venus-heart cockle. The 

 truncated appearance on the one side, and its being carin- 

 ated in the middle, point out a conformation of the inhabi- 

 tant different from the true cockles. Of this new genus we 

 possess some fossil species. 



8. MACTRA. The ligament, in the marine bivalves, is, 

 in general, placed on the outside, but in this genus, of which 

 Lamark has formed his family mactreacea, the ligament 

 is internal, and inserted in a cavity at the hinge formed for 

 its reception. This family, as it stands at present, contains 

 several well characterised genera. 



In the restricted genus, MACTRA, as represented by the 

 M. stultorum of Linnaeus ; the shell gapes a little, and the 

 lateral teeth are strong, and lock into each other. ..Th-j 

 shells with age arrive at a considerable thickness. The in- 

 habitant belongs to the genus callista in the system of Pcli. 



The genus CRASSATELLA of Lamark contains shells which 



