90 THE NAUTILUS. 



NEW SPECIES OF BIFIDARIA. 



BY DR. V. STERKI. 



Bifidaria perversa n. sp. 



Shell sinistrorse, obloug-cylindro conical, horn-colored, trans- 

 lucent; apex rather acute; base umbilicate-rimate, the umbilicus 

 partly overlaid by a projecting part of the last whorl ; whorls 5-', 

 rather slowly and regularly increasing, convex, with the suture 

 moderately deep, the last equaling two-fifths of altitude, slightly 

 narrowed at the periphery, at last somewhat ascending and then 

 protracted horizontally beyond the periphery of the spire, for a 

 length equal to one-third of the diameter, with a rather high, 

 oblique crest-swelling all around, in front of that contracted, and 

 margins broadly everted all around at the aperture ; on the palatal 

 side of the protracted part, behind the aperture, a deep longitu- 

 dinal ( = spiral) impression; surface slightly shining, with fine, 

 almost regular, crowded stria; nucleus microscopically rugulose; 

 aperture of moderate size, rounded below, truncated above, with a 

 sinus occupying the upper half of the palatal side. Lamellae and 

 folds : angulo-parietal large ; angular at its inner end joining the 

 side of the parietal, with a curve reaching the margin at the supero- 

 parietal angle ; parietal very high, strongly curved, the (inner) 

 convexity toward the columella, its front end at a rather large dis- 

 tance from the supero-columellar angle ; columellar spiral, with its 

 front end on the parietal wall, its inner part not visible; basal 

 radial, lamellar, high ; inferior palatal fold very deep in the throat, 

 long, lamellar, curved downward over the basal, visible only from 

 the outside; superior quite short, high, tooth-like, in front of the 

 inferior. 



Alt. 2.-'), diam. of spire 1.1, whole diam. 1.5 mm.; apert. alt. 0.8, 

 diam. O.b' mm. 



H(tbitt. Nogales, Arizona, on the Mexican border. Collected 

 by Mr. E. H. Ashmun, together with Bi.f. Ashm/uni(see below) and 

 the following species: 



Bif. jierrersa is unlike any other species of the genus, by its being 

 sinistrorse and the last whorl protracted considerably beyond the 

 periphery of the spire. In size, shape, color, striation, the con- 



