CARDIUM. 97 



the umbones of a bivalve shell, as distinguished from the 

 lateral teeth, which are placed at a distance on each side. 

 In Venus, fig. 119, the cardinal teeth, are marked by the 

 letter c. 



CARDIOCARDITES. Bl. A genus separated from Cardita, Auct. 

 Thus described (translation) "oval species, with the inferior mar- 

 gin nearly straight, or a very little inflated, crenulated and 

 completely closed. Ex. LaC. Ajar, Adans Seneg. pi. 16. fig. 2." 



CARDISSA. Sw. A genus composed of those species of Cardium 

 Auct. which are heart-shaped. Ex. C clionseum, fig. 122. And 

 C. Cardissa. 



CARDITA. Brug. Fam. Cardiacea, Lam. Submytilacea, Bl.-- 

 Descr. Equivalve, inequilateral, ovate, subquadrate or oblong, 

 marked externally by ribs radiating from the umbones and termi- 

 nating in a crenulated margin on the inner surface ; cardinal 

 teeth in one valve, one long, thick, oblique ; another short, more 

 straight ; in the other valve one long, oblique, thick. Muscular 

 impressions two in each valve, rather oval; palleal impression 

 not siuuated. — Obs. This description includes Lamarck's genus 

 Venericardia, which, although consisting of the more oblong 

 species, is not considered sufficiently distinct to justify the 

 separation. Cypricardia is distinguished from this genus by a 

 remote lateral tooth. Mediterranean, Africa, East Indies, &c 

 Cardita calyculata, fig. 124. 



CARDIUM. Auct. Fam. Cardiacea, Lam. Conchacea, Bl. — Descr. 

 Equivalve, sub-equilateral, sometimes gaping posteriorly, orna- 

 mented on the outside by ribs radiating from the umbones ; 

 cardinal teeth, two in each valve, locked into each other cross- 

 wise, lateral teeth, two in each valve, remote ; muscular im- 

 pressions, two in each valve ; palleal impression entire. Liga- 

 ment external, inflated. — Obs. Although this genus includes 

 many remarkable forms, the characters are so easily defined that 

 there is no difficulty in distinguishing it from any other genus. 

 C. angulatum,fig. 123. C. Grcenlandicum, fig. 123*. Aphrodita, 

 Lea. C. Hemicardium, fig. 123**. fig. 122. C. Dionseum. It is 



H 



