AURIS. 



only moderately curved, the teeth of the median portion of the 

 radula having single, exceedingly long, oblique, blunt or emar- 

 ginate cusps. Neopetrseus. 



a 1 . Apical whorls of the shell sculptured with an exceedingly fine, 

 even grating, formed by minute pits regularly arranged in spiral 

 and vertical series (as in pi. 15, fig. 31). 



b. Periphery of shell angular, or base obliquely truncate or 



flattened ; teeth of the median portion of radula having 



enormously expanded, rounded cusps (entocone and meso- 



cone), and minute, spur-like, basal ectocones; the transverse 



rows V-shaped, running obliquely backward from the middle. 



c. Shell trochiform, smooth, regular. Plaits of the jaw 



vertical and parallel. No entocone appearing on the 



teeth. Oxychona. 



c 1 . Shell with conic spire, the last whorl running upward, 



or obliquely truncate below. Jaw high-arched, with 



narrow converging plaits. Entocone conspicuous on 



the outer lateral and marginal teeth. Zaplagius. 



b l . Shell ovate or oblong. Teeth of the radula excessively 



numerous, with indistinct basal-plates, arranged in variously 



curved rows, but running obliquely forward on each side of 



the rhachis; all the lateral teeth of a peculiar tricuspid form. 



Drymseus. 



a*. Apex of shell nearly smooth, but usually showing some low ir- 

 regular longitudinal wrinkles, and faint, fine, spiral striae. Radula 

 with comparatively few teeth in a transverse row, the rows run- 

 ning a little backward from the rhachis. Lateral teeth having a 

 broad, rounded main cusp and a well-developed ectocone, the 

 marginal teeth much as in Drymceus. Leiostracus. 



Genus AURIS Spix. 

 Manual x, p. 95. Type A. melastoma. Pachyotus of many authors. 



Large, usually pale-colored Bulimulid<B, with the apex smooth, 

 the peristome reflexed and generally bearing a flange or callosity 

 upon the outer lip. 



The genital system, jaw and teeth, present no well-marked or 

 diagnostic characters differentiating this group from Plekocheilas or 

 Bulimvlus. It rests upon conchologic peculiarities. 



