18 STROPHOCHEILUS-BORUS. 



ovate-pear-shaped, acute above; outer lip slightly expanded, much 

 thickened, regularly curved below, straightened above, whitish ; col- 

 umellar lip concave below, passing gradually into the parietal wall 

 above, and making no perceptible angle with it ; broadly reflexed 

 and adnate ; parietal callus white and strong. 



Alt. 60, diam. 37 mill. ; apert, alt. 37, width 28* mill. 



Andes of Eastern Peru (Matthews). 



Helix mathiusii ORB., Guerin's Mag. de Zool. 1835, p. 16. Bul- 

 imus mathiusii ORB., Voy. dans 1'Amer. Merid. p. 303, pi. 38, f. 3, 4. 

 B. matthewsii BECK, Index, p. 53. PFR., Monogr. ii, p. 25 ; iv, p. 

 366. MARTENS, Novit. Conch, v, p. 7. ? Bulinus leucostoma Sows. 

 P. Z.S. 1834, p. 141. PFR., Monogr. ii, p. 23. B. mahoganiSows., 

 Conch. 111. f. 59. 



The comparatively short, blunt, rounded spire is the most prom- 

 inent feature distinguishing this species from the several preceding, 

 with which it shares a pear-shaped mouth, continuous parieto-col- 

 umellar lip, and the long, narrow ribbing of superior whorls. 



The B. lencostoma of Sowerby is believed by Dr. von Martens to 

 be identical. It is from the same collector (the botanist D. Mat- 

 thews, locality Prov. Xagua, Peru), and is described by Sowerby as 

 follows: "Shell ovate, ventricose, wider in front, obtuse behind; 

 whorls 4, the first longitudinally subsulcate, the last large, smooth, 

 olivaceous-brown throughout, the suture paler, crenulated; aperture 

 oblong, acuminate behind, peritreme reflexed, white; length 2'6, 

 width 1'4 inch." This species was afterward figured by Sowerby in 

 the Conchological Illustrations, f. 59, as Bulinus mahogani. 



Granting the identity of the forms described by Orbigny and 

 Sowerby, the question of priority arises. Orbigny's description bears 

 date July 1, 1835 ; Sowerby's, Dec. 9, 1834 ; but as it is known that 

 the Proceedings of the Zoological Society appeared in print very 

 long after the dates of the meetings, there is no conclusive evidence 

 that the name leucostoma has precedence ; and its subsequent disap- 

 pearance from English literature renders its use inadvisable, even 

 if identity with mathiusii were proved, unless its priority be demon- 

 strated. 



S. DURFELDTI Dohrn. PI. 10, figs. 51, 52. 



Shell long-elliptical, yellow-brown, the first whorl smooth ; on the 

 second whorl riblets appear, not crowded, becoming stronger on the 

 third and first half of the fourth, and closer, narrower, somewhat 



