524 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



24; J. P. Iddings. Head of Conant Creek, Teton Range; north of Owl 

 Creek, northeast slope of Teton Range; north end of Teton Range, north 

 of Owl Creek; Snake River Valley, east of Two Ocean Plateau; W. H. 

 Weed. Limestone bluff south side of Soda Butte Creek, northwest of 

 Abiathar Peak; J. P. Iddings. North side of North Fork of Mill Creek, 

 Snowy Range ; Louis V. Pirsson. Under quartzite ridge north side of Burnt 

 Fork. Kinderhook age, Burlington, Iowa; Dry Canyon, Oquirrh Mountain, 

 Utah; Montana. 



Orthothetes sp. 



This species is represented by a single imperfect specimen, which seems 

 to differ from any of the other forms recognized in the collection. It is 

 about the size of Derbya Tteokuk(V), and much larger than Orthotlietes incequalis, 

 but the surface ornamentation is different from either. While the striae in 

 D. keokuk (?) are rounded and contiguous, in this form they are narrow and 

 threadlike, more as in 0. incequalis, the space between any two stria? being 

 wider than the stria? themselves. Thus the surface as a whole is more 

 coarsely striate than in 0. incequalis, although the stria? themseh'es are of 

 the same size and character. 



This form is without the median septum peculiar to the genus Derbya. 



Formation and locality: Madison limestone, head of Conant Creek, 

 Teton Range; AY. H. Weed. 



DFRBYA Waagen, 1884. 



Derbya keokuk Hall (?) 



Orthis crenistria Yandell and Sbuniard, 1849 : Contributions Geol. Kentucky, pp. 19, 21. 

 Orthis keokuk Hall, 1858: Geol. Surv. Iowa, Yol. I, Pt. II, p. 6-40, PI. XIX, tigs. 5a, 5b. 



Keyes, 1895 : Geol. Surv. Missouri, Yol. Y, Pt. II, p. 63. 

 Streptorhynchus keokuk Hall, 1883 : Second Aun. Eept. New York State Geologist, PI. 



XLI, figs. 1-3. 

 Derbya keokuk Hall and Clarke, 1892: Pal. New York, Yol. VIII, Pt, I, p. 262, PI. XI, 



figs. 1-3. 



This form occurs only at a single locality, and the material present is 

 highly unsatisfactory- It seems to be nearer to I), keokuk than to any 

 Strophomenoid shell with which I am acquainted, but its exact generic 

 position can not be ascertained. It is about twice the size of even the 

 largest specimen of Orthothetes incequalis, finely and evenly striate, the stria? 

 round, proximate, and crossed by fine, lamellose, concentric stria?. 



