PLEURODONTE. 85 



Shell imperforate or umbilicate, rather large and solid, varying 

 from globose-depressed to lens-shaped, the periphery rounded or 

 keeled ; surface striate or granular. Whorls 4 to 6. Aperture with or 

 without teeth, the lip more or less expanded or reflexed. Eggs 

 rather large, oval, hard-shelled, the newly hatched young having a 

 shell of 2 to 2 * whorls. Type P. sinuata Mull. (See pi. 22, figs. 1 

 to 10; pi. 25, all figs except fig. 9.) 



Animal having the sole undivided ; lateral edges of foot with no 

 traces of foot margin; tail rounded, convex above; sides of foot 

 with granules arranged in oblique rows or irregular ; back with some 

 indistinct longitudinal lines or none; mantle-edge generally having 

 small body lappets. 



Jaw solid, arcuate, with blunt ends, and either smooth with a 

 slight median projection, weakly ribbed, or with strong rounded 

 ribs on its median moity (plates 21, 24, 26). 



Teeth of radula in nearly straight transverse rows; central and 

 lateral teeth unicuspid, the lateral expansions of the cutting point 

 occupying the place of ectocones, or having side cutting points 

 developed. Marginal teeth either unicuspid or having a bifid meso- 

 cone and a simple or bifid ectocone (plates 21, 24, 26). 



Genitalia : Penis large, muscular, having the retractor and 

 epiphallus inserted at its apex; interior with many longitudinal folds 

 and usually a papilla ; sometimes provided with a short appendix. 

 Epiphallus varying from long to very short, ending in a short 

 flagellum. Female system lacking all accessory organs. 



Distribution, West Indies and northern South America. All of 

 the species are ground snails. 



The essential features of this genus are anatomical : (1) the in- 

 sertion of the retractor on the penis itself; (2) the continuation of 

 the penis in an epiphallus, into which the vas deferens enters, and 

 which terminates in a flagellum ; (3) the entire simplicity of the fe- 

 male system as in Pyramidula or Polygyra ; (4) the rather large, 

 hard shelled eggs; (5) the tendency of the teeth to develop meso- 

 cones at the expense of ectocones. 



The jaw varies from the ribbed (odontognathous) to the smooth 

 (oxygnathous) type. The shell exhibits a wide range of variation in 

 the several sectional groups; but notwithstanding the considerable 

 variations of both shell and soft parts, the genus is a well character- 

 ized one, the forms being unquestionably of common ancestry, al- 



