88 PLEURODONTE. 



incequalis Fiseh., lapicida L., isognomostomos Gin. Pleurodonta 

 BECK, Index Molluscorum p. 33, and of subsequent authors. Den- 

 tellaria SCHUMACHER, Essai d'un Nouv. Syst. des Hab. des Vers 

 Test., p. 69, 230, proposed for D. globularis Sebum, (undescribed 

 and unfigured) and D. sinuata Mull. (1817). Lucerna "Humph." 

 SWAINS., Malacology, p. 329 (in part). Man. of Conch, v. p. 97. 

 Not Lucerna Humphrey, Museum Callonianum p. 61, 1797. 



Shell imperforate or umbilicated, solid, opaque, varying from sub- 

 globose to lens-shaped ; surface densely granulated, at least above. 

 Whorls 4-6, the last deflexed in front. Aperture wider than 

 high ; peristome broadly expanded, toothless or having from one to 

 five teeth upon the basal lip; parietal wall calloused but without 

 teeth. Type P. sinuata Mull. (See pi. 25, figs. 6, 7, P. sloaneana 

 var. vendryesi; pi. 25, fig. 8. P. acuta var nobilis.) 



Animal having the sole undivided, foot edge with no trace of 

 border ; tail rounded behind ; back with a few indistinct grooves from 

 mantle to head, the sides irregularly granulated. 



Genital organs as in Caprinus. Penis stout, cylindrical, the re- 

 tractor muscle and epiphallus inserted at its apex ; epiphallus long, 

 flagellum short. Spermatheca oval, situated on a long duct (pi. 

 24, fig. 5, P. invalida ; pi. 24, fig. 6, P. acuta). 



Jaw arcuate, solid, having unequal, strong, rounded ribs denticu- 

 lating both margins, the ends blunt and free from ribs (pi. 24, fig. 

 4, P. acuta'}. 



Dentition as in Caprinus. Central and lateral teeth having the 

 mesocones large and long, expanded laterally. Marginal teeth 

 having an oblique cusp, formed by the united ento-, meso- and ecto- 

 cones, which are indicated by slight notches (pi. 24, fig. 7, P. acuta'). 

 Distribution, Jamaica. 



Pleurodonte is allied to Caprinus in characters of dentition and 

 genitalia, the anatomical features of the two groups being practi- 

 cally alike. The shell differs from that of Caprinus somewhat in 

 the arrangement of the teeth, which in Pleurodonte are restricted 

 to the basal lip ; but chiefly by the general fades something diffi- 

 cult to define, but readily recognized in the shells themselves. The 

 group is developed with a wonderful exuberance and variety of spe- 

 cific and subspecific forms, perhaps unparalleled in any tract of like 

 extent in the world. The anatomy has been investigated by Sem- 

 per (Reisen), Binney (Ann. N. Y. Acad.), and myself. 





