Length. 



Width 



19.00 



10.00 



16.50 



9.50 



14.50 



8.50 



14.00 



7.50 



12.50 



: 



406 THE CHICAGO ACADEMY OF SCIENCES. 



lus rather heavy in some specimens in which case making a continuous 

 aperture; axis very -lightly twisted ; columella with a well marked 

 fold, more strikingly developed in immature than in very old speci- 

 mens, and frequently indicated only by a tubercle-like swelling. 



Aperture length. Width. 



10.10 5.00 mill. Type. 



9.10 4.80 



8.50 4.00 



3.40 



8.00 3.50 



Types: Chicago Academy of Sciences, five specimens. X< . - 

 Cotypes, collections of Academy of Natural Sciences. Philadelphia 

 and A. A. Hinkley. 



Type Locality : Jackson Lake, drained by the south fork of the 

 Snake River. Wyoming. 



Animal, Jaw. Radula and Genitalia: Unknown. 



Range : Wyoming and Idaho. A species of the Boreal i Canadian ) 

 l ; fe zone and of the Columbian region. 



RECORDS. 



Idaho: Snake River (Dall). 



Wyoming : Jacksons Lake, drained by the south fork of the Snake River ; 

 Phelps Lake, eight miles south of Jacksons Lake ( H. O. Hinkley : A. A. Hink- 

 ley). 



Geological Range: Unknown. 



Ecology : Xot recorded. 



Remarks : This species was received from Mr. A. A. Hinkley of 

 DuBois. Illinois, under the name of binneyi. Comparison with Tryon's 

 types showed at once that it was not that species which is larger, of 

 a different color and with a differently shaped shell, inner lip. umbili- 

 cus, etc. It approaches gabbii Tryon. but the aperture is more regularly 

 elongate-ovate, the zvhorls are rounder, the inner lip is broader, there is 

 an umbilical chink and the whole shell is more fusiform. Comparison 

 has been made with Tryon's types and with a set in the Chicago Acad- 

 emy of Sciences, from the original lot received from Tryon. It has 

 some resemblance to catascopium, but the columella is quite dissimi- 

 lar, there is an umbilical chink, the color of shell and aperture is differ- 

 ent, and the aperture is differently shaped. Jacksonensis has a super- 

 ficial resemblance to sumassi but differs in being shorter and wider. 

 smaller | usually | and with a very different columella i compare the 

 figures of these species on plates XLI and XLII (. The reference by 

 the writer in the Xautilus to Binney's figures of shells from Grind- 

 stone Creek was an error, as these figures refer to apicnia. Jackson- 



