[1] Pilsbry's original text (the type description) reads as follows: The shell is very small, perforate, broadly ovate, corneous, translucent, thin; surface glossy, very minutely marked with delicate growth-lines.

A. N. S. P. This little shell resembles the larger Bythinella palomasensis, from Lake Palomas in northern Chihuahua (NAUTILUS IX, 68, Oct., 1895; Dall, Proc.

Washington county is in the southwestern angle of Utah, drained by the Virgin river, flowing into the Colorado.

All of the adult specimens of A. deserta have the last whorl shortly free at the aperture.

They have apparently never gained access to the small perennial streams of the higher mountains; and permanent springs and streams are so rare on the lower levels that the colonies are small, few and widely separated.

The large proportion of extremely diminutive species in the arid region is remarkable.

dwarfing due to unfavorable conditions.This article incorporates a public domain text from reference.