THE NAUTILUS. 53 



Shell ovately fusiform, solid; color very dark horn; surface shining, 

 lines of growth coarse, crossed by deeply incised spiral lines sagrinat- 

 ing the surface; one or two rest periods are discernible as longitudinal 

 bands on the body whorl or spire; apex smooth, very dark chestnut 

 color; whorls 5, rounded, rather rapidly increasing in size; body 

 whorl large, ovately-inflated; sutures well impressed; spire about 

 equal to the aperture in length, broadly conical; aperture regularly 

 elongate-ovate, narrowed at both ends, somewhat effuse anteriorly; 

 outer lip with a chestnut-bordered internal lip; inner lip in the adult 

 rather broadly reflected over the umbilicus, leaving a small, narrow 

 chink; juvenile specimens are almost imperforate; parietal callus 

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

 peritreme; axis very slightly twisted; columella with a well-marked 

 fold, more strikingly developed in young than in old specimens. 



Length 19.0, width 10.0, aperture length 10.1, width 5.0, mm. 



Length 16.5, width 9.5, aperture length 9.1, width 4.8, mm. 



Length 14.5, width 8.5, aperture length 8.5, width 4.0, mm. 



Length 14.0, width 7.5, aperture length 7.5, width 3.4, mm. 



Length 12.5, width 7.5, aperture length 8.0, width 3.5, mm. 



Types: Chicago Academy of Sciences, 6 specimens. 



Cotypes: Collections of Acad. Nat. Sci., Phila., and of A. A. 

 Hinkley. 



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

 Snake River, Wyoming. 



Records: Oregon: Grindstone Creek (Hayden, Smithsonian col- 

 lection). Wyoming: Jackson Lake; Philips Lake, eight miles north 

 of Jackson Lake (H. O. Hinkley, A. A. Hinkley). 



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

 Du Bois, Illinois, under the name of L. binneyi. Comparison with 

 Tryon's types at once showed that it was not that species, which is 

 larger, of a different color and with a differently-shaped shell, inner 

 lip, umbilicus, etc. It approaches L. gabbi Tryon, but the aperture 

 is more regularly elongate-ovate, the whorls 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 Academy of Sciences received from Tryon 

 from the original lot. The species resembles very closely in color 

 and in the form of the columella certain forms of apicina (=solida 

 preoccupied) but the spire of jacksonensis is longer and the aperture, 

 narrower. 



