lvi 



A DICTIONARY OF TERMS. 



careous, or horny particles, exuding from the 

 mantle, or body, of the Mollusca. It is these 

 particles which form the successive layers that 

 envelope the animal, and constitute the shell. 



K. 



Keel. - - - A term applied to the back of shells that are 

 shaped like a boat. The Chitons are keeled. 

 The Paper nautilus is keeled. 



L. 



Labium. - - See Lip. 



Lamina. - - A plate, or layer. An Oyster-shell heated in the 

 fire separates into laminae, or plates. 



Lateral. - - Belonging to the side. 



Lenticular. - Of a lens shape. The fossil Numularia are 

 lenticular shells. 



Lid. - - - - See Operculum. 



Lip. - - - - The last turn of the spire in Univalves. 



Lip. - - - - The Cowries have two lips, one right, and the 

 other left. 



Lip. - - - - In Bivalves. The exterior edge of the valves. 



Ligament. - A horny substance uniting the valves of shells to- 

 gether at the hinge. Almost all Bivalves are 

 united by ligament. It is interior in Oysters, 

 and exterior in Muscles. 



Linear. - - Very narrow. 



Linguiform. - Tongue-shaped. 



Longitudinal. Lengthwise. The longitudinal measure of a shell 

 in Bivalves, is always from the hinge to the 

 margin, however narrow the shell may be. In 

 Univalves, from the apex to the base. 



M. 



Margin. - . The edge of a shell. Some Bivalve shells have 

 their margins plain, some waved, and others cre- 

 nated, or dentated, &c. 



