1903.] 



NATURAL SCIENCES OF PHILADELPHIA. 



615 



VARIATION IN THE SNAIL-GENUS ASHMUNELLA. 

 BY T. D. A. COCKERELL. 



Dr. Pilsbry's interesting remarks in these Proceedings, 1903, pp. 

 193-200, prompt me to offer some observations on Ashmunella. The 

 species A. ihomsoniana, with its various races or subspecies, inhabits 

 the mountains near Santa Fe and Las Vegas, N. M., and has lately 

 been obtained in sufficient quantities to afford statistical data which 

 may be expressed in curves or polygons. On June 20, 1903, Dr. 

 ^I. Grabham and the present writer collected a large nimiber of A. 

 thomsoniana cooperce on the Kin Kale Ranch, Pecos, N. M. (alt. about 

 6,700 feet), and on plotting out the curves of shell-diameter, it was 

 found that the mode for cooperce fell exactly between thomsoniana 

 proper and porterce, though there was a tendency toward a secondary 

 mode coincident with the normal mode of porterce. The following table 

 makes the facts clear, and can be converted into a series of curves by 

 an}^ one who cares to do so : 



Ashmunella thomsoniana Varieties. 



