18 NOMENCLATURE. 



Columella. Pillar ; the middle column about 

 which the wreaths form their spiral cir- 

 cuit. 



abrupta. Abrupt : truncate at the base. 



caudata. Caudate; elongated so as to project 

 beyond the body. 



plana. Flat ; extending into a plain lip. 



plicata. Plicate ; marked with transverse folds. 



spiralis. Spiral; caudate and spirally twisted. 



Cost^e. Ribs ; keel -like processes reaching from 

 the apex to the periphery of the shell. 



fornicator. Arched ; beset longitudinally with 

 hollow scales. 



Digiti. Claws; digitate or finger-like lobes of 

 the outer lip. 



Dorsum. Back ; the upper part of the body 

 when laid on the aperture. 



Epidermis. Skin: a membranaceous covering 

 of the shell, found on some but not on all 

 species. 



Genicula. Geniculations; the contraction 

 of the whorls so as to correspond with the 

 internal divisions or dissepiments. 



