146 BULIMULUS-BOSTRYX-PERON^EUS. 



B. TSCHUDII Troschel. PL 45, figs. 32, 33. 



Shell perforate, oblong, the apex attenuated, rather acute ; some- 

 what smooth or striate, opaque, whitish, sometimes with brown 

 bands of dots. Whorls 7-8, convex, the last somewhat compressed 

 in the middle, one-third the entire length. 



Aperture oval-oblong ; peristome simple, not expanded, the mar- 

 gins converging ; right margin curved above, produced forward ; 

 columellar margin short, subvertical and dilated. 



Alt. 9, diam. 3 mill. ; aperture, alt. 2| mill. (Pfr.). 



Huaura and Huacho, Peru, on walls (Ttchudi). 



Balimus tschudii TROSCHEL, Archiv fiir Naturg., 1852, i, p. 195, 

 pi. 5, f. 7. PFE., Monogr., ii, p. 163 (1848) ; vi, p. 103. 



This species is especially distinguished by the compression of the 

 last whorl. All of the specimens collected, about 30 in number, 

 were so characterized ; and in most of them the compression was so 

 great that the whorl could not be called convex, and an indication 

 of two faint keels was mentionable. Most of the specimens wen' 

 weathered and had lost their color, wholly or in part. On some 

 could be seen that on a yellowish translucent ground, there are very 

 irregular, white, opaque flecks ; that further, a few irregular longi- 

 tudinal brown streaks occur ; and that there are narrow, brown 

 interrupted spiral bands, three on the upper, six on the last whorl. 

 {Troschel}. 



Group of B. williamsi. 



B. WILLIAMSI Pfeiffer. PL 46, figs. 37, 38, 39. 



Shell imperforate, subulate, rather solid, striatulate ; white, 

 painted with deep chestnut streaks, darker and closer below ; spire 

 turrited, the apex obtuse. Whorls 8, rather flat, the last not one- 

 third the entire length, compressed at base. 



Aperture slightly oblique, oblong ; peristome simple, not ex- 

 panded, the margins subparallel, columellar margin thin, adnate. 



Alt. 24, diam. 6i mill. ; aperture 7 mill, long, 3 wide. (Pfr.). 



Catamarca, Andes of Peru (Williams). 



Bui. williamsi PFR., P. Z. S., 1858, pi. 257, pi. 42, f. 1 ; Malak. 

 BL, 1859, p. 44 ; Monogr., vi, p. 108 ; Novit. Conch., iii, p. 467, pi. 

 101, f. 24, 25. 



Judging from what I have seen, this species is sometimes decol- 

 late and plugged like a Cylindrella. Such a specimen before me 



