NOMENCLATURE. 35 



Labi um Lip 5 the internal or columellar mar- 



interius. gin of the aperture. 



In the Patellae this name is given to a 

 testaceous membrane in their concavity 

 QdW^dfornicale when under the vertex, and 

 laterale when it constitutes a chamber in 

 the side. 



exterius. The outer margin of the aperture. 



anticum. Anterior part ; next the spire. 



posticum. Posterior; that nearest the rostrum. 



coarctatum, Coarctate ; drawn back to the 

 base. 



digit atum. Digitate; divided into attenuated di- 

 verging lobes. 



solutum. Disengaged; separated from the whorls 

 by a sinus or gutter. 



fissum. Cloven ; silmost divided in the middle by 

 a linear sinus. 



mucronatum, 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 horny, testaceous, 

 d2 



