DESCEIPTIONS OF SPECIES. 345 



1883. Orthis earbonaria. Hall, Rept. New York State Geol. for 1882, pi. (7) 37, tigs. 1-4. 

 Coal Measures: Springfield, 111. 



1883. Orthis pecod. Kayser, Richtofen's China, vol. 4, p. 177, pi. 24, fig. 1. 

 Upper Carboniferous: Lo-Piiig, China. 



1884. Orthis pecosii. Waagen, Paleontologica Indica, ser. 13, \oL 1, p. 573, pi. 56, figs. 13a-13e. 

 Lower Productus limestone: Salt Range, Amb., India. 



1884. Orthis pecosi. White, Geol. Surv. Indiana, 13th Rept., p. 129, pi. 32, figs. 20-22- 



Coal Measures: Horse Shoe of Little Vermilion and Garret's Mill, Vermilion County, Ind. ; Ver- 

 milion County, 111. 



1892. Rhipidomella pecosi. Hall and Clarke, Pal. New York, vol. 8, pt. 1, pp. 210, 226, pi. 7, figs. 1-4. 

 Coal Measures: Near Springfield, 111. 



1895. Orthis pecosii. Keyes, Missouri Geol. Surv., vol. 5, p. 64. (Date of imprint, 1894.) 

 Coal Measures: Kansas City, Mo. 



1896. Orthis pecosii. Smith, Am. Phil. See, Proc, vol. 35, p. 237. 

 Upper Coal Measures: Poteau Mountain, Ind. T. 



1900. Rhipidomella pecosi. Beede, Univ. Geol. Surv. Kansas, Rept., vol. 6, p. 90. 



Upper and Lower Coal Measures: Fort Scott, Kansas City, Eudora, Lawrence, Lecompton, Kans. 



M}' material is, as a rule, rare and not well preserved, but the species has been 

 obtained from near Glenwood Springs (station 2329b) in fair abundance and preserva- 

 tion. Specimens attain a size greater, somewhat, than that figured by Marcou, and 

 a length of 14 millimeters seems to be about normal for the specimens seen by me, 

 which agree in this and other particulars, so far as I have been able to ascertain, 

 with the species as it is represented in the Missis.sippi Vallej^. 



A ver}^ poor specimen from Leadville (station 2259), which seems to have been 

 originally identified as Derbya crasna, probably belongs to this species. 



Locality and horizon. — Leadville district (stations 2259, 2264); base of the Weber 

 formation. Grand River region, Glenwood Springs (station 2329b). San Juan 

 region (2186?); Molas formation. 



ORTHOTICHIA Hall and Clarke, 1892. 



Okthotichia schuchertensis n. sp. 



PI. I, figs. 16 to 16b. 



Shell of medium size, transver.se. Dorsal valve strongl}^ convex; beak large 

 and incurved; area small (?); fold broad and scarcely appreciable; anterior outline 

 emarginate. 



Ventral valve smaller and shallower than the dorsal; beak probably incurved 

 and not quite as projecting as the other; sinus broad and strong, especially toward 

 the front. This valve is provided with a rather thick, but not very high, median 

 septum reaching about one-third the distance toward the anterior margin, and by a 

 pair of strong dental lamellae. 



The surface is marked by very slender, equal, radiating striae and by much 

 stronger ones regularly' distributed among them. The latter are discontinuous and 



