BULIMULUS-BOSTRYX. 133 



This shell belongs to the same group as the preceding, but differs 

 in certain particulars. The most noticeable is the ornamentation of 

 the surface, which consists of elevated distant, curved ribs, like those 

 of a Scala. These ribs begin on the third whorl, the summit being 

 smooth and corneous. Very pronounced at the beginning, the ribs 

 enlarge and become wider spaced with the increase of the shell, are 

 continued into the umbilical cavity and persist to the extreme limit 

 of the shell. The intercostal spaces have lower, finer riblets. An- 

 other differential character is the form of the aperture. Not only 

 is the cavity narrower than in other species of this group, but the 

 margins are united above, as though the peristome were continuous. 

 The outer lip is narrow ; it surpasses the columellar margin, the 

 dilation of which is very weak, sometimes almost absent. Umbilicus 

 strictly analogous to that of tubulatus and infundibulum. The 

 whorls of the spire also have a peculiarity ; the earlier are rounded, 

 but little by little the convexity diminishes, and toward the middle a 

 contraction becomes quite noticeable. This causes a sort of indis- 

 tinct bulging below the sutures, which gives the spire a turriculate 

 appearance. (Morel.'). 



Section 3. Bostryx Troschel (s. str.), 1847. 



Bostryx TROSCH., Zeitschr. f. Mai., 1847, p. 49 (April, 1847), type 

 and sole species B. solutus. 



Shell turrited, higher than wide, rugose, the last whorl or two either 

 free, not in contact, or separated by very deep sutures. Aperture small, 

 squarish-oval, subvertical ; umbilicus inconspicuous. Type B. 

 solutus Troschel. 



B. SOLUTUS Troschel. PI. 44, figs. 99, 1, 2. 



Shell turrited, rather thin, rugose ; ashen, usually two-girdled with 

 chestnut. Spire turrited, the apex rather obtuse. Whorls 6, the 

 upper four regularly in contact, the latter two completely free, not in 

 contact, the right side above and the base keeled, the keel bordered 

 by an impressed line on each side. 



Aperture subvertical, oblong-tetragonal (or quadrangular), the 

 angles of left side rounded ; peristome simple, straight, continuous. 

 Alt. 12, diam. 5? mill.; aperture, alt. 4, width 3 mill. (Pfr.). 



Peru (Dr. v. Tschudi). 



Bulimus (Bostryx} solutus TROSCH., Zeitschr. f. Mai., 1847, p. 49 ; 

 Archiv fur Katurg., 1849, i, p. 233, pi. 4, f. 5 (dentition) ; and 1852, 



