PART II. HELICIN^. 331 



HemicycJa Sw. Shell discoid ; spire rather flattened, 

 but not small, and of four whorls ; outer lip semicir- 

 cular, dilated into a broad, flat margin, but not re- 

 flected ; inner lip nearly obsolete, but sometimes 

 with a small obsolete tooth ; umbilicus none ; sur- 

 face distinctly striated. 



H. plicaria. En. Meth. 462. f. 3. 



Helix And. Body- whorl ventricose ; spire more or less 

 conic, but always shorter than the aperture ; umbili- 

 cus almost always closed, or not existing ; outer lip 

 reflected or thickened. 



pomatia. Chem. 128. f. 1138. hoemastoma. Ch. 130. f.ll50. 

 aspera. Penn. pi. 87. f. 3. melanotragus. En. Meth. 



lactea. Chem. 1 20. f. 1 1 6 1 . 462. f. 4. 



Zonites Montf. Shell sub-ventricose, but the body- 

 whorl depressed, the margins convex ; spire often of 

 many whorls ; outer lip thin ; umbilicus open, 

 unizonalis. En. M. 462. f. 6. citrina. Chem. 131. f. 1177. 



Epistyla Sw. Shell very thick, conic, and obtuse ; the 

 whorls very numerous ; body-whorl and aperture 

 small ; outer lip thin. 



E. conica Sw. Sow. Man. f. 281. 



Streptaxis Gray. Heliciform ; but the pillar or axis 

 not perpendicular, which gives the body-whorl a dis- 

 torted appearance ; umbilicus small, open ; spire of 

 six whorls ; outer lip thickened. 



S. contusa Gray. Sow. Man. f. 269, 270. 



Geotrochus Sw. Shell somewhat spiral; the spire 

 being conical, often trochiform, and always longer 

 than the aperture, which is transverse and without 

 teeth. 



Hemitrochus Sw. Whorls convex ; spire conic, obtuse, 

 not longer than the aperture ; outer lip having a 

 thickened rim inside the margin, which is acute ; 

 umbilicus closed. 



H. hoemastomus Sw. {See Jig. 19. p. 165.) 



