78 University of Michigan 



Distribution: Aruba; very rare; 6 specimens under lime- 

 stone rocks at type locality. 



Shell (fig. xv-56) : small, sub-discoid, rather heavy; dark 

 horn-colored. Whorls: 4i^, markedly flattened above but 

 scarcely subangulate ; gradually increasing ; suture deeply im- 

 pressed vertically; last whorl slightly descending. Sculpture 

 of last whorl : closely spaced, compressed, undulate and rarely 

 anastomosing, cuticular riblets, which are slightly more ob- 

 lique than (and cross) the obscured growth wrinkles. Penul- 

 timate whorl: in addition, with the broken bases of what, in 

 young specimens (fig. xv-55), are long (.33 mm.), sparsely 

 and irregularly scattered, white hairs, which extend even into 

 the umbilicus. Embryonic whorls : I14 ; with regular, some- 

 what heavier, cuticular costae, which are slightly more oblique 

 than the obscured growth wrinkles and extend to the very 

 apex. Umbilicus : large, about 3/10 the major diameter of the 

 shell; circular. Aperture: oblique, subcircular. Peristome: 

 incomplete, very slightly thickened ; parietal callus very weak. 



Measurements 



altitude maj. diam. min. diam. alt. apert. diam. apert. whorls 



2.09 190(3.93) 160(3.38) 61(1.27) 140(1.76) 4i^ 



These shells are certainly very closely related to Tri- 

 chodiscina crinita Fulton (1917; P. Mai. Soc, XII, 240), 

 from Carthagena, Colombia. However, the Aruba form is evi- 

 dently a larger shell (even after making allowance for the 

 greater number of whorls) ; its last whorl is markedly flattened 

 above instead of evenly convex; the incomplete peristome is 

 slightly thickened ; and the parietal callus is very weak, almost 

 absent (from Fulton's figure, it would appear that the peri- 

 stome of his shell is continuous, but I suspect that it simply 

 has a heavy, parietal callus). Both crinita and arubana must 

 have similar sculpture to that in Trichia venezuelensis 

 Jousseaume (1889; Mem. Soc. Zool. France, II, p. 248, figs. 

 ix-12, 13) and Trichia rojasi Jousseaume {I.e., p. 249, figs. 

 ix-9, 10), both from Venezuela; although venezuelensis is 

 described as hirsute, the figure of rojasi is the one that shows 



