218 THE CHICAGO ACADEMY OF SCIENCES. 



SHELL: 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 

 4*/2, 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 



8.00 6.20 6.00 " 



9.00 6.00 5.75 3.00 " Ogalalla, Neb. 



10.00 6.50 6.00 3.50 " New Mexico. 



11.00 7.50 6.00 3.75 " 



12.50 9.50 8.00 5.00 " Rio Puerco, N. M. 



13.50 9.50 8.25 5.00 " 



TYPES: Academy of Natural Sciences, Philadelphia, four speci- 

 mens, No. 84287. 



TYPE LOCALITY: Las Vegas, New Mexico. 



ANIMAL : Not examined alive. 



JAW : Like that of cubensis. 



RADULA: Formula: T l3 r +t+}-f-j : +J-ff-h J L? T (21-1-21) ; similar 

 to that of cubensis. (See pi. 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 pi. XI, fig. A.) The penis is a trifle stouter than in cubensis. 



TABLE OF MEASUREMENTS. 1 



Prost. Penis- 



Penis. Penis-sac. Vas. del duct. Rec. sem. Pen. ret. sac. ret. Shell. 

 1.00 1.50 6.75 1.50 1.75 .60 .75 6.00 



RANGE (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 



'Dissection No. 23919. 



