116 CONCHACEA. 



described in this family are divided into three seetions. First, 

 those which are regular, and have distant lateral teeth, Cardium, 

 Donax, Tellina, Lucina, Cyclas, Cyprina, Mactra, and Erycina. 

 Second, those which are regular, and have no distant lateral 

 teeth, Crassatella and Venus. Third, those which are irregular, 

 Venerupis, Coralliophaga, Clotho, Corbula, Sphsenia, and Un- 

 guium. 

 CONCHACEA. Lam. A family of Lamarck's order Conchifera 

 Dimyaria. Regular, unattached in general, closed at the sides. 

 They are always more or less inequilateral. The Marine Con- 

 chacea are those which inhabit the sea. The fluviatile Conchacea 

 are those which are found in rivers, ponds, &c. Each of these 

 contain various genera, which may be arranged as follows : — 



Fluviatile. 



1 . Cyrenella. Three cardinal teeth ; ligament long ; shell 

 thin. Fig. 114. 



2. Cyclas, Thin, oval ; cardinal and lateral teeth ; anterior 

 side shortest, including Per a. 



3. Pisidium. The same, with the posterior side shortest. 

 Fig. 112. 



4. Cyrena. Thick; cardinal and lateral teeth. Fig. 113. 



5. Potamophila. Two thick cardinal teeth. Fig 115. 



Marine. 



1. Cyprina. Two cardinal teeth, and one remote lateral 

 tooth. Fig. 116. 



2 Venus. Three cardinal, no lateral teeth ; including Ar- 

 temis. Fig. 118, 119, \\9a. 



3. Cytherea. Several cardinal teeth ; one very short lateral 



tooth. Fig. 117, 117«, 1175, 117c, 117^. 



4. Fullastra. Cardinal teeth notched, otherwise like Venus. 



Fig. 120. 



5. Astarte. Three cardinal teeth ; ligament short. Fig. 



110. 

 Venericardia belongs to the Cardiacea. 



