26 CHAMA. ARCA. OSTREA. 



The Spondyli are frequently found attached to 

 rocks at some depth in the ocean. The animal is 

 eaten on the coasts of the Mediterranean. We 

 have no British Spondyhis, 



" Chama. Shell thick ; hinge -with a thick 

 tooth, sometimes crenate, obliquely inserted into 

 a corresponding channel. (Plate 5.) The shells 

 of this genus vary greatly, which you will per- 

 ceive upon comparing C. gigas and C. cor. (See 

 Plate 9, Isocardia cor.) The Chama genus is 

 usually ribbed, foliated, or scaly. C. Lazarus 

 is a beautiful species : C. cor is a British species, 

 and the only one. The whole number is twenty- 

 five. 



" Here is Noalis-ark, an example of the genus 

 Area, and is found on our own coasts. The long 

 hinge beset with sharp teeth, inserted into each 

 other, renders the genus sufficiently marked ; but 

 in some species the hinge is curved. The form 

 varies exceedingly. The number of species is 

 forty-five. (Plate -5.) 



" Ostrea. In this well-known genus we lose 

 sight of the toothed hinge. Take that PecteJi, 

 or scallop, which belongs to one division of Ostrea 

 in this system, and tell me what holds the valves 

 together. Charles is silent ; what says Lucy ?" 



'^ Here are the remains of the same kind of 

 substance which we saw in Donaco and in Venus. 

 I think it is called the ligament.''' 



