EXPLANATION OF TERMS. 219 



site to the apex. In bivalve shells that 



part of the margin which is opposite to 



the beaks. 

 Bivalve. A shell with two valves; from bis, 



twice, and valve. 

 Bifid. Cleft in two ; from bis, twice, and fid i, 



I have cleft. 

 Bifurcated. Having a fork of two teeth ; from 



bis, twice, and furc a, a fork. 

 Branchiae. Gills; from the Greek /-fyayxta, 



(branchia) the gills of fish. 

 Cardo or Hinge. In bivalves, that part of the 



circumference where the valves cohere. 

 Carinate. Furnished with a keel-like elevated 



ridge; from carina, a keel. 

 Columella. The pillar round which the whorls 



form their spiral circuit; from columella, 



a little column. ;* 

 Convoluted. Rolling regularly over each other ; 



from con, together ; and volut us, rolled. 

 Cephalopodes. Having feet on the head ; from 



the Greek /ce^aX^, (cephale) a head, and 



7ro&$, (podes) feet. 

 Cephala. Having a head ; from the Greek 



K<pahy (cephale) a head. 

 Corneous. Horny ; from cornu, a horn. 

 Crenated. Notched ; from cren a, the notch of 



an arrow. 

 Coriaceous. Like leather ; from cori um, skin, 



leather. 

 Callosity. Hardness of skin or flesh ; from 



call us, which has the same signification. 



