212 MEXICAN OPEAS. 



This species imitates the contour of 0. micro,, but it differs 

 conspicuously from that in the dense, sharp sculpture. Fig. 

 68, of pi. 28 represents a specimen from Texolo, pi. 40, fig. 9, 

 a larger one from Orizaba, type locality. 



17. 0. YUCATANENSE n. sp. PI. 28, fig. 69. 



Shell very narrowly rirnate, cylindric-turrite, thin, pale 

 yellowish corneous, subtransparent, the axis showing faintly 

 through. Surface glossy, very finely, weakly striatulate. 

 Spire straightly tapering to the very obtuse summit. Whorls 

 6 l /2, tumid just below the deeply impressed suture, elsewhere 

 moderately convex. Aperture subvertical, trapezoidal-ovate. 

 Columella subvertical, with narrowly reflexed edge. Length 

 6.5, diam. 1.9, aperture 1.9 mm. 



Yucatan: Ticul (Heilprin exped., 1890). 



This cylindric-tapering form has a deep but narrowly im- 

 pressed suture, the whorl below it rising steeply. The sur- 

 face is more glossy than 0. gracile and much less sharply 

 striate. I have not been able to compare 0. rarum, but with 

 the same number of whorls that is a longer shell. 



18. 0. SEMISTRIATUM (Morelet) . PL 29, figs. 84, 85. 



Shell narrowly and deeply rimate, subelongate-couic, thin, 

 minutely striate, hyaline, pale corneous-whitish. Spire ob- 

 long-conic, the apex rather obtuse. Suture deeply impressed. 

 "Whorls 7, a little convex, the embryonic 2 smooth, the third 

 and fourth having rather wide-spaced riblets, which disap- 

 pear on subsequent whorls; last whorl inflated, shorter than 

 the spire; columella, nearly straight, whitish. Aperture acu- 

 minate-oval, colored within like the outside ; peristome simple, 

 the margins joined by a thin callus; columellar margin di- 

 lated, partly covering the umbilicus, basal and outer mar- 

 gins acute. Length 12, diam. 5, aperture 4.5 mm. long, 

 scarcely 3 wide (C. & F.). 



Mexico: Forest of Palenque, in the State of Chiapas 

 (Morelet). 



Bulimus semistriatus MORELET, Testae, novissima ii, p. 10 

 (1851). PFR., Monogr. iii, 441. Bulimulus s., CROSSE et 

 FISCHER, Moll. Mex. p. 555, pi. 20, f. 14, 15 (description and 

 figures of type). Opeas s., MARTENS, Biologia, p. 296. 



