VITRINID^E. 137 



Subgenus PARMACOCHLEA, Smith, 1884. 



Animal as in Parmarioii. Shell almost concealed, flattened, 

 oblong, having the nuclear portion in the form of a minute 

 Sigaretus-like shell projecting from beneath. 



Genus ASPIDELUS, Morelet, 1883. 



Animal limaciform, posteriorly dorsally carinated with a 

 caudal mucous pore ; shield moderate, gibbous, with slightly free 

 margin ; pulmonary orifice at the middle of the right margin of 

 the shield. 



Shell external, mytiliform, not spiral. W. Africa* 



Genus VITRINOZONITES, W. G. Binney, 1879. 



Shell elongated, submembranaceous. Animal with round 

 caudal mucous pore, bordered by a simple transversely grooved 

 rim, covered completely when closed, when open the cover raised 

 into a sharp carina. No appendiculate mantle-lobe. Marginal 

 teeth unicuspid, instead of bicuspid, as in Yitrina (PI. 29, 

 fig. 10). 



One species, mountains of E. Tennessee and W. North Caro- 

 lina. 



Genus YELIFERA, W. G. Binney, 1879. 



Shell subglobose, smooth, shining. Animal furnished with 

 accessory mantle processes covering most of the shell; mucous 

 pore a simple slit, without horn-shaped process. Jaw smooth, 

 infeiiorly produced in the middle. Marginal teeth bifid (PL 29, 

 fig. 11). 1 species. Costa Rica. 



Genus HELICARIOX, Ferussac, 1821. 



Shell Yitriniform, rounded oval, thin and fragile, covered 

 with a very thin epidermis ; whorls few, rapidly increasing, the 

 last much swollen ; aperture large, with simple, sharp peristome. 



Animal not entirely retractile within the shell ; mantle pro- 

 duced in front into two lobes upon the neck, with a posterior 

 lobe on the right side, partly covering the shell ; foot truncate 

 behind, with a dorsal projection and mucous pore, the sole 

 longitudinally divided into three parts. Marginal teeth biouspi- 

 date (Dentition, PI. 29, fig. 12 ; jaw, PI. 29, fig. 13.) More than 



