9() THE NAUTILUS. 
NEW SPECIES OF BIFIDARIA. 
BY DR. V. STERKI. 
Bifidaria perversa n. s}). 
Shell sinistrorse, oblong-cylindro conical, horn-colured, trans- 
lucent; apex rather acute; base umbilicate-rimate, the umbilicus 
partly overlaid by a projecting part of the last whorl; whorls 53, 
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 striz; nucleus microscopically rugulose ; 
aperture of moderate size, rounded below, truncated above, with a 
sinus occupying the upper half of the palatal side. Lamellee 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. 2.5, diam. of spire 1.1, whole diam. 1.5 mm.; apert. alt. 0.8, 
diam. 0.6 mm. 
Habitat.—Nogales, Arizona, on the Mexican border. Collected 
by Mr. E. H. Ashmun, together with Bif. Ashmuni (see below) and 
the following species: 
Lif. perversa 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- 
