Genus 4. 

 CARDIUM. 



GENERIC CHARACTER. 



Animal Tethys. 



Testa bivalvis, subrequilatera, aequivalvis. 



Cardo dentibus raediis binis alternatis ; lateralibus remotis, insertis. 



Animal a Tethys. 



Shell bivalve, nearly equilateral, and of equal valves. Hinge with two 



primary teeth, alternating with the opposite; lateral teeth remote, 



and inserted. 



GENERAL OBSERVATIONS. 



Bruguiere observes, that Langius, who is the first 

 Testaceological writer upon whose nomenclature any 

 dependance can be placed, has described all the shells 

 of this genus, under the collective title of Concha; cor- 

 diformes. D'Argenville, afterwards, adopted the de- 

 nomination of this author, and gave the name of heart 

 to every shell bearing any external resemblance to that 

 organ. 



But the generic character of Langius is insufficient, 

 since it does not apply to every species of the genus ; 

 and that of D'Argenville is excessive, since it not only 

 includes the Cockles, but also such shells of the genus 

 Chama, Area, and even Venus, as have any tendency to 

 the shape of a heart. 



This genus, such as Linnaeus has left it in the twelfth 

 edition of his Sy sterna Natures, is founded on the num- 



