FAMILY OF CHAMAUEA. 



Fig. 101. UNIO. 



We also place in this same group certain marine mollusks, 

 which resemble the Unios in their organization and the general 

 disposition of the hinge, but in which the beaks (summits) of 

 the shell are more arched, and from which projecting ribs 

 radiate towards (he circumference; such are the genus CAR- 

 DITA, the form of which is more or less oblong- or cordiforrn 

 (heart-shape) ; the CYPRICARDIA, in which the tooth beneath the 

 summit of theshell isdivided intotvvoor three; the CORALLIOPHAGA, 

 in which the shell is thin and the lateral plate much effaced, &c. 



26. In the FAMILY OF CHAMACEA the mantle is closed 

 and perforated by. three open- 

 ings only; through the anterior 

 one passes the foot (fg. 102, 

 p) ; the next (r) gives passage 

 to the water necessary for res- 

 piration, and the third (e) is 

 for the expulsion of effete 

 matters. As we have already 

 stated, the last two openings 

 are not prolonged into tubes, T l< 

 as in the next two families. 

 And the hinge is very analo- 

 gous to that of the Unios ; for 

 the left valve has a tooth near 

 the summit, and further back, a projecting plate, which are re- 

 ceived into fossae (pits) in the opposite valve. 



Explanation of Fi>. 102. A Chama divested of its shell to show the dis- 

 position of its mantle : p. the foot ; r. opening for respiration ; c the 

 opening for the passage of excrement. 



26. What are the characters of the family of Charaa'cea? 



ax* 



:HAMA, WITHOUT ITS SHELL. 



