444 CAEBONIFEKOUS FORMATIONS AND FAUNAS OF COLORADO. 



18S7. Macnidmi lenuUtriata. Herrick, .Sci. Lali. IJenison Univ., Bull., vol. 2, p. :51. 



Coal iMeasures: Flint Kidge, Ohio. 

 1888. ihicrodon. (allieil to) trmiLiiriata. Herrick, ^ci. Lab. Denison Univ., Bull., vol. 4, pi. 10, lig. lr>. 



Waverly group: Cuyahoga Falls, Ohio. 



1895. Macrodoii fciiiiistrialus. Keyes, Missouri Gieol. Surv., vol. 5, p. 120. (Date of imprint, 1894.) 

 Upper Coal Measures: Kansas City, Mo. 



189G. Macrodon tenuUtriatus. Smith, Leland Stanford Junior Univ. PuljL; Cont. Biol. Hopkin.« Seaside 

 Lab., No. 9, p. .34. 



Upper Coal Measures: Poteau Mountain, Indian Territory. 



1896. Macrodon tenuislriaius. Smith, Am. Phil. Soc, Proc, vol. 35, p. 244. 

 Upper Coal Measures: Poteau 'Mountain, Indian Territory. 



This species is represented by a single poor specimen which seems to have been 

 the basis for the citation of this species in the lists of the Leadville monograph." 



Locality and horizon. — Leadville district (station 2275); upper portion of the 

 Weber formation. 



PLEUROPHORUS King, 1844. 

 Pleukophorus subcostatus Meek and Worthen. 



1865. Pleurophorus subcostatus. Meek and Worthen, Acad. Nat. Sci. Philadelphia, Proc, p. 246. 

 Upper Coal Measures: North branch of Saline Creek, Gallatin County, 111. 



1866. Pleurophorus subcostatus. Meek and Worthen, Gieol. Surv. Illinois, Eept., vol. 2, p. 347, pi. 27, 



figs. 2, 2a. 



Upper Coal Measures: North branch of Saline Creek, Gallatin Count}', 111. 

 1887. Pleurophorus subcostatus f Herrick, Sci. Lab. Denison Univ., Bull., vol. 2, p>. 35, pi. 4, figs. 16, 16a. 



Coal Measures: Flint Eidge, Ohio. 

 1900. Pleurophorus subcostattis. Beede, Univ. Geol. Surv. Kansas, Kept., vol. 6, p. 161, pi. 20, figs. 11-llb. 



Upper Coal Measures: Kansas City, Mo. 



That part of the material in our collections which belongs to the genus Pleuro- 

 phorus has proved most perplexing. The dispositions which I have made in the way 

 of specific discrimination seem to be the best under existing conditions, but they are 

 far from satisfactor3\ The material from each locality is generally scanty, and the 

 preservation varies both in character and degree of perfection. 1 have not been able 

 to satisfy myself in what measure the many differences which have been noted are 

 due to preservation and what to specific ditferentiation. 



The prevailing form in the Rico formation is closely related to PI. subcostatus. 

 Two examples of this form are shown on PI. IX, figs. 11 and 12. These specimens, 

 however, are smaller than others occurring in the black siliceous limestone of this 

 formation, while in the red calcareous sandstones thej^ grow still larger, some indi- 

 viduals attaining a width of 43 mm., agreeing with the smaller forms, meanwhile, 



nU. S. Geol. Surv., Mon., vol. 12, 1886, p. 70. 



