466 University of Kansas Geological Survey. 



being short, and, like the lateral margins, more or less digitate. 

 Greatest diameter of the specimen, retaining only a small por- 

 tion of the non-septate outer whorl, four and four-tenths inches ; 

 greatest convexity of the same, ninety-five hundredths of an 

 inch ; breadth of umbilicus, one and thirty-five hundredths 

 inches ; breadth of the last whorl from the siphonal to the um- 

 bilical side, one and eight-tenths inches." 



Additional description by Stanton : "In the young stages of 

 this species the costse are simple, linear, closely arranged, and 

 strongly curved forward. The keel is then minutely crenate, 

 with one crenation to each costa. After the third volution, 

 some of the costse are more strongly developed and bear nodes 

 or small spines at their outer ends, while the intermediate ones 

 become obsolete. The crenations of the keel still continue nu- 

 merous and small. ... It can be easily distinguished 

 [from P. Wyoming ensis] by its more compressed form, by the 

 greater regularity of the costoe, and by the much greater differ- 

 ence between its young and adult stages." 



A single specimen from Williams' Butte, Mitchell county, in 

 the Septaria horizon. 



Prionotropis woolgari Man tell. Plate en, figs. 1-4. 



Ammonites tuoolgari Mantell, 1822, Geol. of Sussex, p. 197, pi. xxn, ff. 6, 7; 



Sowerby, 1829, Min. Conch., vol. vi, p. 25, pi. dlxxxvii, f. 1; Sharpe, 1853, 



Fossil Remains Moll. Chalk of England, p. 27, pi. n, ff. 1, 2; Meek and 



Hayden, 1861, Proc. Acad. Nat. Sci. Phil., p. 421. 

 Prionocyclus (Prionotropis) woolgari Meek, 1876, U. S. Geol. Surv. Terr., 



vol. ix, p. 455, pi. vu, ff. la-h, and pi. vi, f. 2. 

 Ammonites percarinatus H. & M., 1856, Mem. Am. Acad. Arts and Sci., 2d 



ser., vol. v, p. 396, pi. iv, f. 2. 



Prionotrojiis woolgari Stanton, 1892, Bull. U. S. Gsol. Surv. No. 106, p. 174, 



pi. XLII, ff. 1^:. 



Meek's description: "Shell attaining a medium size, more 

 or less compressed-discoidal, the outer turn being proportion- 

 ally more convex (including nodes) than those within; um- 

 bilicus about equaling the greater dorso-ventral diameter of the 

 last turn ; each volution embracing about one-fifth of the next 

 Avithin, and having its umbilical margin slightly indented by 

 the uncovered nodes forming the inner of the two outer rows on 

 the succeeding; volution within. 



