NOMENCLATURE. 19 



Labium. Lip; the internal or columellar mar- 



interius. gin of the aperture. 



In the Patellae this name is given to a 

 testaceous membrane in their concavity 

 called fornicale when under the vertex, and 

 laterale when it constitutes a chamber in 

 the side. 



exterius, Labrum. The outer margin of the aper- 

 ture. 



anticum. Anterior part; next the spire. 



posticum. Posterior ; that nearest the rostrum. 



coarctation. Coarctate : drawn back to the base. 



digitatum. Digitate ; divided into attenuated 

 diverging lobes. 



solutum. Disengaged ; separated from the whorls 



by a sinus or gutter. 

 Jissum. Cloven ; almost divided in the middle by 

 a linear sinus. 



rnucronatum. Mucronate ; projecting in one sin- 

 gle sharp point. 



Operculum. Lid; a plate or door with which 

 some species close the aperture of their 

 shells : it is either of a hornv, testaceous, 



