ZOOLOGY. MOLLUSCA. 195 



PffiCILOZONITES. 



Generic characters: Shell helicoid, subtrochiform, depressed 

 conic, or subdiscoidal, perforate or umbilicate, obliquely striate, 

 ornamented with radiating zigzag flammules or spiral bands 

 of chestnut color on a lighter ground ; whorls numerous (7-10) ; 

 very slowly widening; body-whorl more or less flattened or 

 compressed below the usually carinate periphery, not descend- 

 ing anteriorly; aperture more or less irregularly lunate; peris- 

 tome simple, the columellar margin slightly expanded and 

 thickened with a white callus which encircles the pillar within. 

 Animal similar in form to Helix ; foot narrow, short posteriorly, 

 scarcely reaching behind the shell, and without longitudinal 

 furrows above its margin or caudal mucous pore ; orifice of geni- 

 tal ia on the right side of neck, near to, but not under, the mantle; 

 mantle margin simple; jaw like that of JAmax, very thin, 

 arcuate, with a broad blunt median projection anteriorly ; 

 radula with tricuspid central teeth having quadrate basal 

 plates, the central cusps projecting beyond the anterior mar- 

 gins of the basal plates, the side cusps rather short, with well 

 reflexed cutting points ; lateral teeth similar but asymmetrical, 

 lacking the inner cusps ; marginal teeth aculeate, with simple 

 thorn-shaped cusps and oval basal plates. ' 



It will be seen by the above definition that the genus cannot 

 be included in any of the groups with which its species have 

 been associated by authors ; the zonitoid dentition at once re- 

 moves it from the Helicidx, and the absence of a caudal 

 mucous pore, the more anterior position of the orifice of the 

 genitalia and the coloration of the shell, separate it from 

 Zoniies and its subgenera. 



The relationship of the species of Poecilozonites to one an- 

 other is shown by the similarity of the radula} and jaws, and 

 of the external characters of the animal; in the shells, 

 which at first glance seem to be a heterogenous assemblage, by 

 the callus which coats the columella, the compression of the 

 whorl below the periphery, and especially by the color-pattern, 



