188 POLYMITA. 



N. Y. A cad. Sci. iii, p. 89 (Jaw and dentition). POEY, Memorias 

 sobre la Hist. Nat. Cuba, ii, pi. 7, f. 5. PILSBRY, Man. Conch., v, 

 p. 52. 



Shell subglobular, brilliantly colored, rather thin but solid, imper- 

 forate ; whorls few (about 4), the last but little deflexed ; aperture 

 rounded, slightly lunate, the peristome simple, not expanded or re- 

 flexed except at axis, where it is reflexed and adnate over the umbil- 

 ical region ; axis solid. Type P. picta, pi. 56, fig. 10. 



Animal (of P. p!da) black above, slaty below; evenly granulated 

 throughout, without dorsal grooves, facial groove or foot margin, 

 the tail rounded above, not grooved; sole not in the least divided, 

 mantle edge thickened but without lobes. 



Jaw arcuate, moderately solid, smooth (PI. 51, fig. 8, P. picta). 



Radula short and wide, the teeth all of the same form, and in 

 \-shaped rows, formula about 85.1.85. Basal plates long and narrow; 

 cusps situated far backward, and projecting well over the posterior 

 margin; all teeth tricuspid, the three cusps united into a broad, tri- 

 dentate gouge-shaped cutting edge. (PI. 51, fig. 5, central with four 

 lateral teeth; fig. 6, group of outer laterals; fig. 7, two extreme 

 marginal teeth of P. picta'). 



Genital system (pi. 51, fig. 4, P. picta} altogether like that of 

 Cepolts. The vagina is long, with a long stalked .spermatheca ; 

 dart sack large, its head marked off by a constriction and united by 

 connective tissue with the vagina; at root of d. s. there is a mucus 

 gland composed of two oval, flat glandular lobes. Penis slender, 

 willi a long flagellum, and apparently no retractor muscle; eye- 

 stalk retracted between branches of genitalia. 



Distribution, Cuba. Habits arboreal. 



The- shell in this group resembles that of Hemitrochus, except 

 that the lip is neither expanded nor thickened within. The genital 

 system is entirely that of Hemitrochus. The radula is excessively 

 peculiar in having the side cusps as long as the middle cusp and 

 united with it to form a broad, tridentate gouge, all three cusps be- 

 ing subequally developed on all the teeth. 



This type of radula may be compared with that of Orthalicus, 

 Oxychona, I'H/JU/IKI, and especially with Amphidromus; all being 

 arboreal genera, which have independently evolved the same gen- 

 eral type of teeth. 



