THE NAUTILUS. 



141 



taken last October at Trinidad, in southeastern Colorado, by Mr. 

 J. H. Ferris9 and the senior author. 



BlFIDARIA AGNA n. Sp. 



The shell is rimate, cylindric, the last three whorls of about equal 

 diameter, the summit very obtuse ; surface nearly smooth; of a sperm- 

 aceti-whitish color. There are 4| convex whorls, the last with a 

 strong rounded crest behind the outer lip, rather close to it above, 

 but being more oblique, it is further behind the lip at the base. 

 Behind this crest the whorl is a little flattened laterally, and shows 

 the lower palatal plica, though as a white spot. The aperture is 

 brought forward nearly in line with the ventral convexity of the 

 whorls. The peristome is thin, slightly expanded, strengthened a 

 short distance within with a low callous rib. The parietal lamella 

 appears distorted and angular in front view ; seen from the base it is 

 seen to consist of an angular and a parietal lamella, completely 

 united inwardly. The columellar lamella is sinuated or bent and 

 strongly developed. The basal fold is strong, arising on the callus 

 but extending inward beyond it. The lower palatal fold is large and 

 pliciform, more or less immersed, standing chiefly inward from the 

 palatal callus. The upper palatal fold is much smaller, and stands 

 rather near the lower, upon the palatal callus. There is a small or 

 minute suprapalatal fold, also on the callus. 



Length 1.75, diam. 1 mm. 



Trinidad, Colorado, type no. 93052 A. N. S. P. ; also Silver Lake, 

 Kansas. 



This species resembles some forms of B. pentodon (Say), especially 

 those from northern Alabama, in which the lower palatal fold is long 



