206 SOUTH AMERICAN OPEAS. 



tatica di terra e di acqua dolce dell' Argentinia meridionale, 

 1874, p. 27, pi. 1, f. 5. 



This form has, if the figure is correct, shorter whorls than 

 0. gracile, while the general shape is similar to that species. 

 An indigenous Opeas would hardly be expected to occur 

 around Buenos Ayres; and I suspect that when specimens are 

 compared, 0. martensi will turn out to be one of the numerous 

 aliases concealing Opeas gracile. The type figure is copied 

 on my plate. 



10. 0. PELLUCIDUM (Pfeiffer). PL 29, fig. 80. 



Shell subperforate, turrite, very thin, striatulate, glossy, 

 pellucid, buff-corneous. Spire long, the apex obtuse. Whorls 

 7, a little convex, the last one-third the total length. Colu- 

 mella somewhat twisted; aperture squarish oval; peristome 

 simple, acute the columellar margin shortly revolute. 



Length 11.5, diam. 4, aperture 4x2 mm. (Pfr.). 



Colombia: province of Merida (Funck; Cuming coll.). 



Bulimus pellucidus PFR., P. Z. S. 1847, p. 231; Monogr. 



11, p. 156. REEVE, Oonch. Icon, v, pi. 68, f. 487. 



This shell seems to have the texture of the more lengthened 

 0. octogyrum. I have not seen it. 



11. 0. OCTOGYRUM (Pfeiffer). PI. 29, figs. 75 to 79. 



Shell imperforate, subulate, thin, rather smooth, pellucid, 

 waxy- whitish. Spire long, the apex obtuse ; suture margined. 

 Whorls 8, flattened, a little swollen at the suture; the last 

 whorl about one-fourth the total length, slightly tapering 

 basally. Aperture oblique, oblong, the peristome simple, un- 

 expanded, the right margin arched forward above ; eolumella 

 thread-like, slightly arcuate. Length 12.5, diam. 2.66; aper- 

 ture 3 x 1.5 mm. (Pfr.). 



Venezuela: Caracas (E. Klocke). 



Bulimus octogyrus PFR., Malak. Bl. iii, 1856, p. 45 ; Monogr. 

 iv, 458. Opeas o., STREBEL, Beitrag Mex. etc., v, p. 107, pi. 

 7, f . 20, 6 ; pi. 17, f . 29. 



"This species, according to Pfeiffer's type specimen (pi. 29, 

 fig. 79), comes near to 0. subula in general structure of the 



