214 TERTIARY PERIOD. 



breadtli of body- volution, nine millimeters ; apical angle varying from forty 

 to forty-five degrees. 



Position and locality. — The type-specimens of Meek and Hayden were 

 obtained from Tertiary strata, near Fort Union. Ours are from strata of the 

 same period, Wales, Utah. 



Family VIVIPARID^. 



Genus VIVIPARUS Moutfort, 1810. 



Viviparus trochiformis Meek and Hayden. 



Pl.ate XXI, fig. 4 a, i, and c. 



Paludina trochiformis Meok and Hayden, 1856, Proc. Acad. Nat. Sci. Phlla., 122. 



Vivq)arus trochiformis Meek, 1872, Geol. Siirv. Montana, Idaho, Wyoming, and Utah, 



478. 



Shell trochiform ; spire somewhat broadly conical ; apex acute ; volu- 

 tions five or six, moderately convex, marked by a greater or less number of 

 slightly raised revolving lines ; the last volution angular or abruptly 

 rounded below the middle ; suture linear, usually indistinct, especially 

 between the larger volutions, but rather more distinct between those near 

 the apex ; aperture subcircular or subtetrahedral ; lip thin, reflexed against 

 the columella in front, by which a small umbilical suture or groove is pro- 

 duced ; columella arcuate. 



This species presents considerable variation in form and appearance, 

 and also in the character of the revolving lines ; upon some examples these 

 fines are few and indistinct, especially upon the body-whorl, but upon 

 others they are numerous, and sometimes one or two of them are found to 

 assume the character of small carinse. 



Surface marked also by the ordinary lines of growth. 



Length, about twenty-three millimeters ; breadth of body-whorl, eight- 

 een millimeters ; apical angle, about seventy-five degrees, but the spire is 

 a little convex-conical. 



Position and locality. — Strata of Tertiary age at the following localities 

 in Utah: Last Blufi"; Ephraim City; south of Last Bluff; east of Joe's 

 Valley; and at the head of Soldier's Fork. 



Viviparus trochiformis, var. 

 Plate XXI, fig. 5, a and b. 



Associated with typical forms of V. trochiformis at a locality south of 



