368 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



From the first, it differs clearly in the strongly flexuous nature of its costye ; 

 and from the latter, not only in that character, but in having only one instead 

 of several plaits on the columella. The Indian species also attains a larger 

 size, and has more distant vertical costa?. Neither the Indian nor the Lim- 

 bourg species belongs to the genus Valuta, but, along with Fasciolaria assimilis, 

 Stoliczka, and perhaps some of the Grosau species, fall into the same section 

 or group as the species here under consideration. 



Locality and position. — Yellowstone River, 150 miles from its mouth; 

 where it occurs in beds containing a blending of the fossils of the Fort Pierre 

 and Fox Hills groups of the Upper Missouri Cretaceous. 



Genus PYROPSIS, Conrad. 



Synon. — Tudicla, &c. (sp.), of some (not of Bolteu). 



Pyropsis, Conrad (1860), Jour. Acad. Nat. Sei. Pbilad., IV, 288 (as a subgenus uuder Tudicla); 

 and (lees') Am. Jour. Conch., IV, 248 (as a genus).— Meek (1804), Smithsonian Check- 

 List N. Am. Cret. Fossils, 23 (us a subgenus under Tudicla). 



Papa, Stoliczka (1868), Palseont. Indira. 11, 152 (uot Klein and otheis). 



Etym. — Pyrum, a pear; oipie, form. 



Type. — Tudicla (Pyropsis) perlata, Conrad. 



Shell pyriform; spire much depressed, not papillate at the apex ; body- 

 volution very gibbous, and provided with revolving, generally nodular, or 

 perhaps rarely subspiniferous carinas, suddenly contracted below into a long, 

 slender, straight, or somewhat twisted canal ; axis more or less perforated ; 

 outer lip beveled at the edge, and smooth within ; inner lip thin, rather 

 widely spread on the body-volution, but raised into a more or less prominent 

 fold or projection nearly opposite the base of the aperture, below which point 

 it stands free from the umbilical perforation, or slit, and umbilical ridge, some- 

 limes developing a small callus, or ridge, at the top of the aperture. 



This genus seems to be quite nearly related to Tudicla, Bolten, but 

 differs in having the apex of its spire not papillate, the outer lip smooth 

 instead of striated or suleated within, and more revolving ridges on the body- 

 volution. From Busycon of the same author, which also has the apex of the 

 spire slightly papillate in young examples, it differs in that character, as well 

 as in its perforate axis, and free inner lip below the prominence of the colu- 

 mella,* as well as in generally having more revolving ridges around the 

 body- volution. 



Dr. Stoliczka has referred to the genus Rapa several Indian Cretaceous 

 forms that seem to me, as already intimated, to belong to this group. I cannot 



w In Bwycon, tin- inner lip is closely anchylosed to the columella all Ihc way down the canal. 



