INVERTEBRATE PALEONTOLOGY. . 54;') 



from Quaternary or the latest Tertiary beds. A single fossil species, appar- 

 ently of this genus, described here, came from the latest Cretaceous or the 

 oldest Tertiary of the Upper Missouri. If it really belongs to this genus, it 

 would be the most ancient species yet described, so far as I am informed. 



V i t r i 11 a ! obliqna, M. & H 



Plate 42, figs. 10, «, b. 



Vitrina ? obliqna, Meek and Hayden (1857), Proceed. Acad. Nat. Sci. Philad., IX, 134. 

 Helix obliqna, Meek and Hayden (1860), ib., 431. 



Shell obliquely subovate, or depressed-subglobose ; spire depressed; 

 volutions four, increasing rapidly in size, especially the last one, convex above 

 and below, and more narrowly rounded on the outer side ; suture well 

 defined; umbilical region (in casts) impressed, or very slightly perforated ; 

 aperture subcircular ; surface unknown. 



Height, 0.48 inch ; breadth, 0.66 inch. 



The only specimens yet seen of this shell are mere sandstone-casts, and 

 all more or less distorted. The typical figured specimen has much the gen- 

 eral aspect of a Vitrina; but other more distorted specimens, apparently of 

 the same species, unquestionably have the aperture somewhat contracted, 

 the lip reflexed, and the spire more elevated. If these really belong to the 

 same species, it would not agree with the genus Vitrina. As it is not possible, 

 with such specimens as have yet been found, however, to determine satis- 

 factorily its generic characters, it is here retained doubtfully under that genus. 



The figured specimen of this species probably has its spire a little 

 depressed accidentally. Indeed, I have sometimes suspected that all of the 

 specimens referred more or less confidently to this species may possibly 

 be only distorted examples of the form described in another place under the 

 name Helix vetusta. 



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

 group; probably belonging to the closing part of the Cretaceous period. 



Genus HYALINA, Ferussac. 



Synoii.—Hi/aliua, Ferussac* (1819), Prodr., 40.— Rang (1829), Man., 163 (section of Helicella).— Gray (1840), 

 Turton's Man. (2d ed.), 165; and (1842) Synon. Brit. Mas., 90.— Albers (1850), Die 

 Hiliceen, 66; and (1866) ib. (von Marten's ed.), 67.— Bland (1864), X. Y. Lye. Nat. 

 Hist., VIII.— Morse (1864), Jour. Portland Soc. N. Hist., I, 12.— Tryon (1866), Am. 

 Jour. Coucb., II, 241 aud 246.— Biuuey (1869), Land and Fresh-water Shells N. Am., 

 29.— Gould (1870), Invert. Mass. (Binney ed.), 394 ; and of many others (not of Schum., 

 1817, or Studer, 1820). 



* Fe'russac, I believe, at first wrote the name Hyaline. 

 09 H 



