ORYZOSOMA. 163 



rostrum; columellar margin slightly thickened and very 

 lightly twisted spirally, truncate at the base. Length 21, 

 diam. 10.33, aperture 10x5.5 mm. (Marts.). 



Eastern Costa Rica: Uiskar, in Alta Talamanca (Pittier). 



Streptostyla (Pittieria) bicolor MARTS., Biologia, Moll., p. 

 617, pi. 44, f. 6 (Jan. 1901). 



Genus ORYZOSOMA Pilsbry. 



Orizosoma PILS., Nautilus, v, p. 9 (May, 1891). Oryzo- 

 soma PILS., Proc. A. N. S. Phila. 1891, p. 311 (Aug. 25, 1891). 



Shell ovate-turrite, perforate, the columella concave, cal- 

 loused on the face. Apical whorls smooth, the first 1% glo- 

 bose, the next whorl very narrow. Otherwise as in Strepto- 

 styla. Type 0. tabiense. 



This group was based upon a small shell resembling Strep- 

 tostyla except in having the axis distinctly perforate and the 

 columella not twisted spirally, though there is the almost im- 

 perceptible trace of a fold at its upper insertion. 



1. 0. TABIENSE (Pilsbry). PI. 30, figs. 99, 1. 



The shell is narrowly perforate, ovate-conic, thin but mod- 

 erately solid, weakly striatulate, glossy. The spire is conic 

 with obtuse apex. The first 1% whorls are rather large and 

 very convex; the next % whorl is extremely narrow; sub- 

 sequent whorls increase slowly and are moderately convex. 

 Suture moderately impressed. The last whorl is oval, convex 

 at the base, and impressed around the umbilicus. The aper- 

 ture is vertical, piriform, half the length of the shell. Outer 

 lip arched forward in the middle, not retracted basally. The 

 columella is concave below, straightened above, its edge rather 

 heavily calloused. The upper end of the callus partially fills 

 the mouth of the narrow umbilicus. Length 9.9, diam. 4.9, 

 length of aperture 5 mm. ; whorls 6. 



Yucatan: Hacienda of Tabi, in a cave (Heilprin exped.). 



Streptostyla (Orizosoma) tabiensis PILS., Nautilus, v, p. 9 

 (May, 1891) ; Proc. A. N. S. Phila. 1891, p. 311, pi. 15, f . 6, 7. 



Only a single dead, white specimen was found, but it is, 

 so far as I can see, an uninjured, normal shell, differing con- 



