548 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



It is not possible to determine beyond doubt, from the specimens we 

 have yet seen, whether this species is a true Hyalina or a member of some 

 of the allied groups. As near as can be determined from our specimens, it 

 agrees rather nearly, in form and size, though the transverse striae on the 

 upper side of the whorls are rather stronger and more regular than we 

 usually see in that genus. Impressions left upon internal casts show that 

 the lip is thin and simple. 



In its general appearance, this species resembles Helix omphalus of F. E. 

 Edwards (Monograph Eocene Moll., part ii, p. 69, pi. x, fig. 5, Palaeont. Soc), 

 but its spire is rather more depressed, and the volutions more prominent near 

 the umbilicus, while its aperture is broader and less sinuous on the inner 

 side. It seems not to be very nearly allied to any of our recent species, and 

 is quite unlike any of the other fossil forms )et known from the Upper Mis- 

 souri rocks. 



Locality and position. — Mouth of Judith River, Montana ; from the 



Judith River estuary beds, probably belonging to the latest member of the 



Cretaceous. 



Hyalina! Evan si, M. & H. 



Helix Ecansi, Meek and Hayden (1660), Proceed. Acad. Nat. Sci. Pbilad., XII, 175. 



Fig. 68. Fig. 69. Fig. 70. Shell small, depressed-subglobose ; volutions four 



CZ-'O *" "USu'f'^w-®^ ant ^ a na ^ *° ^ ve ' narrovv > an d a little convex above, 

 rounded on the outer side, and ventricose below ; each 



Hi/alina Evansi. 



Fig. 68. A side view, show- turn slightly embracing on the upper side, and below 

 ing aperture and spire. CO veriiisr nearly the whole breadth of the next one 



Fig. 69. Upper side. / 



Fig. 70. Under side, show- within; umbilicus moderate, or in some instance 



ing umbilicus. . . r ., , j •■ ■, c ,i 



appearing as it it had been covered ; surtace apparently 

 smooth ; aperture obliquely lunate-semicircular. 



Height, 0.18 inch ; breadth, 0.30 inch. 



This species may be readily distinguished from the last by its more 

 deeply embracing whorls. This latter character gives quite a different form 

 to the aperture, which is much narrower and more arcuate than that of H. 

 occidentalis. The shell under consideration also has a rather more prominent 

 spire, and about one whorl more, although smaller than the last. The only 

 three specimens seen are casts of the interior, with some of the thin shell 

 remaining. Two of these show some appearance of having the umbilicus 

 occupied by a lump or callus ; but this may be merely some foreign body, 



