69 



CHAPTER XV. 



OP THE CHAMA. GENUS Xn. 



CHAMA. 



"Animal a Tethys. Shell bivalve, rather coarse; hinge with a callous 

 gibbosity obliquely inserted in an oblique hollow ; anterior slope closed." 

 — Linn. 



Xhe shells arranged in this genus vary very much in their 

 general shape and appearance, as well as in their teeth. Many 

 species are rough with spines, or with leaf-like scales, as Chama 

 Lazarus and gryphoides ; some have longitudinal ribs or ridges 

 like the Cardia, as in Chama antiqiiata and calyculata ; these 

 last have a short thick tooth under the beak, and a longitudinal 

 ridge under the cartilage in one valve, and a hollow under the 

 beak and two longitudinal ridges in the other valve under the 

 cartilage ; but the ridge under the cartilage in Chama Gigas 

 and Hippopus is not very long. When the valves are shut to- 

 gether in Chama Gigas there is an aperture left on that side 

 of the beaks called the posterior slope; but in Chama Hippopus 

 the valves shut close, without leaving any aperture. 



The interior surface of the valves of Chama Gigas and Hip- 

 popus have only one muscular impression on each ; most pro- 

 bably the animals of these are a species of Scallop or Oyster ; 

 the rest of the species have two muscular impressions on each 

 valve. The animals are supposed to be Cockles. 



