176 PALJilONTOLOGY. 



within; columella provided with one rather strong oljlicjue fold below, and 

 a much smaller less oblique one about half-way up the aperture. 



Length, about 0.77 inch; breadth, 0.50 inch; apical angle nearly regu- 

 lar, divergence about 80°. 



I know of no other shell so nearly allied to this as to render a com- 

 jjarison necessary. Its most striking character is the presence of the little 

 folds around the upper part of its body-volution and on those of the spire. 

 These will at once distinguish it from any type of the Melanqnna; known to 

 me, even in specimens not in a condition to show any of the other char- 

 acters. 



Locality and position. — The only three specimens of this species I have 

 seen were found by Colonel Simpson's party in the brackish-water carbon- 

 aceous beds at the mouth of Sulphur Creek, on Bear River, Utah. 



OEIUPHASIIDR^. 



Pyrgulifera humerosa. Meek.* 



Plate 17, figs. 19, 19 a, and wood-cut fig. 6. 

 Melania humerosa, Meek (18G0), Proceed. Acad. Nat. Sci., XII, 313. 

 Tiara humerosa, Meek (ISGG), in Conrad's Smithsonian Check-List of Eocene and Oligo- 



cene Fossils, 12. 

 Pyrpdifera humerosa. Meek (1872), iu Dr. Hayden's Second Ann. Report Geol. Survey 



of the Territories, 294 and 299; and (1876) iu Col. Simpson's lieport Expl. 



across the Great Basin of Utah, 3(i3, pi. v, tig. G a, b, e. 



Shell attaining a rather large size, moderately solid, ovate-subfusiform; 

 spire prominent, distinctly turreted; volutions five and half to about seven, 



*This genus is related to Lithasia, as originally defined by Professor Haldeman, 

 and presents the following characters : 



Shell subovate, thick, imperforate; spire produced, turreted; volutions angidar, 

 shouldered, and nodular above ; surface typically with vertical ridges and revolving 

 markings; aperture subovate, faintly sinuous, but not notched or distinctly angular 

 below ; outer lip prominent iu outline below the middle, retreating at the base, and 

 subsiiuious at the termination of the shoulder of the body-volution above; jjcristome 

 continuous; inner lip a little callous below, and thickened all the way up, but without 

 a protuberant callus above, sometimes with a shallow umbilical furrow along its outer 

 margiu below. 



Ditfers from Lithasia, Haldeman, in not having its aperture distinctly angular 

 and notched, or subcanaliculate below, iu wanting a protuberance at the top of the 

 inner lijt, and in having a more produced, distinctly turreted spire, as well as very 

 ditferent surface markings. 



