218 THE CHICAGO ACADEMY OF SCIENCES. 
Seti: Subglobose, rather thick; color pale horn; surface dull 
to shining; growth lines fine, coarser on the last whorl, which is some- 
times malleated near the aperture ; nucleus very small, rounded ; whorls 
414, very convex, rapidly enlarging; spire very short and broad; last 
whorl very large, globose; sutures impressed; aperture varying from 
ovate to roundly ovate, occupying from two-thirds to two-fifths the 
length of the shell; inner lip broadly expanded, arched over the um- 
bilical chink, which is widely open. 
Length. Breadth. Aperture length. Breadth. 
10.00 7.20 6.70 mill. Type Las Vegas, N. M. 
8.30 6.00 5.30 m y “ 
8.00 6.20 6.00 a ss a ie 
9.00 6.00 5.75 3.00. © Ogatlalla, Neb. 
10.00 6.50 6.00 HA New Mexico. 
11.00 7.50 6.00 Se OS uy 4 
12.50 9.50 8.00 OO: Rio Puerco, N. M. 
13.50 9.50 8.25 | 47 m 
Types: Academy of Natural Sciences, Philadelphia, four speci- 
mens, No. 84287. 
Type Locauiry: Las Vegas, New Mexico. 
AniMAL: Not examined alive. 
Jaw: Like that of cubensis. 
Raputa: Formula: ¢%4+-$4$444$4442¢% (21-1-21) ; similar 
to that of cubensis. (See pl. VII, fig. F.) The marginals are more 
generally serrated than in cubensis, otherwise the teeth are the same. 
In cubensis, however, the intermediate teeth begin on the seventh tooth, 
while in cockerelli they begin on the eighth tooth. In one specimen 
the tenth tooth had a bifid entocone. 

GENITALIA: In almost all respects similar to. those of cubensis. 
(See pl. XI, fig. A.) The penis is a trifle stouter than in cubensis. 
TABLE OF MEASUREMENTS.* 
Prost. Penis- 
Penis. Penis-sac. Vas. def. duct. Rec.sem. Pen.ret. ssac.ret. Shell. 
1.00 1.50 6.75 1.50 Te .60 a5 6.00 
Rance (Figure 18): Montana south to southern Texas; South 
Dakota and eastern Texas west to California. 
The range of cockerelli includes portions of the Upper and Lower 
Mississippian, Rio Grandian, Coloradoan and Californian regions. It 
also appears to inhabit nearly the whole of the great plains area pene- 
trating into the prairie region on the eastern border of its range to the 
95th degree of longitude. The range of cockerelli overlaps that of 
techella on the south; it has the most northern range of any member of 
1Dissection No. 23919. 
