1897.] NATURAL SCIENCES OF PHILADELPHIA. 479 



face slightly shining, very finely and closely costulate-striate through- 

 out, the costulse clear-cut but minute, about 5 in the space of a 

 millimeter, on the last whorl ; becoming lower and fainter on the 

 base. Whorls 6 to 6J, convex, at first slowly, then more rapidly 

 increasing, the last decidedly wider than the penultimate, rounded 

 at the periphery, obtusely angular around the somewhat funnel- 

 shaped umbilicus. Aperture rounded lunate, oblique ; outer and 

 basal margins of peristome slightly expanded, columellar margin 

 dilated above ; basal margin slightly bent forward in the middle. 



Alt. 13 - 5, greater diam. 21, lesser 18*3 mm.; width of aperture 

 11, height 9"5 mm. 



Alt. 12*5, greater diam. 20'5 mm. 



Province of Bahia, Brazil. 



Resembles S. Spixianus in form, but the series of a half dozen spe-' 

 cimens before me differs constantly from that species in the smaller 

 size of the shells and the extremely fine striation. 



S. decussatus n. sp. 



Shell depressed -turbinate, narrowly umbilicate, the umbilicus deep 

 and well-like, one-ninth or one-tenth the diam. of shell ; moderately 

 solid ; pale yellowish. Surface glossy, closely and finely costulate 

 above, the costulre wider than the intervals, about three in the space 

 of a millimeter, and decussated by numerous fine spirals, which cut 

 or indent them but do not appear in the intervening grooves ; the 

 base similarly but less strongly costulate. Spire low conoid, with 

 the lateral outlines but slightly convex, apical whorls costulate; 

 whorls 6J, at first slowly, then more rapidly widening, the last 

 bluntly but conspicuously angular at the periphery, convex beneath, 

 angular around the umbilicus. Aperture rhombic, somewhat ob- 

 lique, angular at middle of outer margin and at junction of the 

 basal with the columellar margin; peristome unexpanded, becoming 

 slightly so below, the columellar margin vertical, dilated above, 

 impinging upon the umbilicus. 



Alt. 16, greater diam. 22, lesser 20 mm.; width of aperture 12, 

 height 11 mm. 



Brazil. 



Peculiar in the decussated sculpture and continuation of the cos- 

 tulation to the apex. The angular periphery and verge of the nar- 

 row umbilicus are also conspicuous features. 



