K4 PROCEEDINGS OF THE ACADEMY OF [18^3. 



some specimens. Dimensions as follows, being the measurement 

 of ten (10) specimens, all adult : 



Longitude -14, Latitude -08 inch. 



The mean of the above measurements is eighteen-hundredths of 

 an inch in length by ninet3'-six-thousandths of an inch in breadth, 

 or very nearlj* two to one. The largest specimen measured ^23 

 V)y •I 3 inch. Aperture about one-third the length of the shell, 

 being as forty-one to one hundred and twenty (xVo)- ^^ the 

 sixteen specimens examined ^ nine are from Pyramid Lake (Clark), 

 and seven from Walker's Lake (Call). 



The Pyramid Lake lot, from Mr. Clark, were accompanied by 

 specimens of the flat-spired form of Pompholyx effusa, to which 

 Dr. Dall has given the name of " var. soliday ^ 



The several specimens of Pyrgula Nevadensis exhibit similar 

 differentiation as Tryonia in size of mouth, variability in coil, 

 robustness or attenuation ; and many of the specimens from the 

 alkaline deposit of the lake bottom are discolored, varying from 

 light ashen slate to dark slate, approaching black. 



In connection with the above, I have to thank Professor Call 

 for the following notes : 



•' I have it as collected by the U. S. Geological Survey the past 



1 Subsequently thirty-two specimens, adolescent and mature, from the 

 dredging "(1) " Pyramid Lake ; and about the same number, young and 

 adult, from "(2)" North Shore, Pyramid Lake, were received from Prof. 

 Call and examined with care. 



■' Annals of Lyceum of Nat. History of N. Y., March, 1870, p. 334. 

 The locality here given, through some misapprehension, is "Clear Lake," 

 which is in California; it should read "White Pine, Eastern Nevada. ' 

 Dall, in Science, vol. i, No. 7, page 202 (March 23, 1883), refers to the 

 occurrence of PompJiolyx effnsa in a calcareous deposit in Pyramid Lake, 

 and remarks on its variations. 



