TERTIxVRY PERIOD. 211 



Physa pleromatis White. 

 PlateXXI, fig. 1 aandi. 



Shell large, ovoid, ventricose ; test thin ; spire short ; whorls five or 

 six, moderately convex, last one inflated; sutui'e distinct, somewhat im- 

 pressed ; aperture narrowly subovoid, slightly arcuate, its length nearly 

 equal to three-fourths that of the shell ; columella a little twisted, so as to 

 produce a slightly prominent fold. Surface rather smooth, but marked by 

 the usual lines of gi'owth. 



Length, thirty-two millimeters ; greatest breadth, twenty-two milli- 

 meters. Some fragments indicate that the shell often reached a still greater 

 size. 



This species differs fromP. Bridgerensis Meek in its more robust foi-m, 

 shorter spire, more ventricose outer whorl, and in having the upper part of 

 its aperture less acutely angular. It closely resembles the recent species 

 P. Sayi Tappan, but the outer whorl of our shell is rather more ventricose 

 and the aperture proportionally narrower, especially its anterior portion. 



Position and locality. — Tertiary strata ; Last Bluff, Utah. 



Suborder GEOPHILA. 



Family HELICIDiE. 



Genus HELIX Liunreus, 1758. 



Helix Leidyi Hall and Meek. 



Plate XXI, iig. 3 a, h, and c. 



Helix Leidyi Hall and Meek, 1856, Mem. Amer. Acad. Arts and Sci., v, new series, 394. 



- Shell rather large, subglobose in form ; spire moderately elevated ; 



volutions about six in mature shells, ventricose, especially the outer one ; 



suture distinct, that of the outer volutions more or less impressed ; umbilicus 



small, probably nearly closed ; aperture obliqvie, broad-subovate in outline ; 



outer lip apparently reflexed ; surface marked by very numerous uniform, 



distinct, closely-arranged lines of growth and also by occasional shallow 



wnnkles. 



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

 obtained from the Eocene Tertiary strata, near the head of Bear Creek, 

 Mauvaises TeiTcs, Nebraska. Ours were collected at Moo-se-ne-ah Peak 

 and Pownsagunt Plateau, Utah. 



