DESCRIPTIONS OF SPECIES. 285 



In the San Juan region (at .station.^ 2370 and 2382) occur.s somewhat scantilj^ a 

 little Productus, of the mra tj'pe which, because of its associations, I have referred 

 to P. liemcosfa. It resembles in every essential specimens from Yellowstone Park 

 belonging to White's species, and is chiefly peculiar for its rarity and its small size. 

 Twelve millimeters is the transverse diameter of the largest specimen seen, and only 

 three or four have come to hand. Into the synonj^my of this species I have intro- 

 duced several refei-ences withdrawn from the Pennsylvanian species, P. cora. Proba- 

 bly several other citations of /■'. cora (or P. j^ratteniayius) from Mississippian horizons 

 should be removed to the synonymy of this species. It is possible, however, that 

 Productus leevicosta is a synonym of Z*. cora. 



Locality and horizon. — San Juan region (stations 2379, 2382); Ouray limestone. 



SPIRIFER Sowerby. 181.5. 



Sl'IBIFER CENTRONATUS Winchell. 



1865. Spirifera centronala. Winchel!, Acad. Nat. Sci. Philadelphia, Proc, p. IIS. 

 Marshall group: Cuyahoga Falls and Akron, Ohio. 



1874. Spirifer centronala. White, U. S. Geog. Geol. Surv. W. lOOthJIer., Prelim. Kept. Invert. Foss., p. 17. 

 Subcarboniferous: Mountain Spring, Old Morman road, Nevada. 



187.5. Spirifer centronatus. White, U. S. Geog. Geol. Surv. AV. 100th JNIer., Kept., vol. 4, p. 86, pi. 5, 

 figs. 8a-8c. (Whole volume published in 1875. ) 

 Subcarljoniferous: Mountain Spring, Old Morman road, Nevada. 



1875. Spirifera (Trixjonotreta) hiplicata. (Hall?) Meek, Pal. Ohio, vol. 2, p. 290, pi. 14, fig. 5. 

 AVaverly group: Richfield, Ohio; Iowa. 



1877. Spirifera centronala. Hall and Whitfield, U. S. Geol. Expl. 40th Par., Kept., vol. 4, p. 254, pi. 4, 

 figs. 5, 6. 

 Near base of Wasatch limestone (Waverly?): Dry Ganyun, Oquirrh Mountains; Logan and 

 Ogden Canyons, Wasatch Kange, Utah. 

 1899. Spirifer centronatus. Girty, U. S. Geol. Surv., Mon., vol. 32, pt. 2, p. 547, pi. 70, figs. 3a-3d. 



Jladison limestone: Yellowstone National Park. 

 1901. Spirifer centronatus. AVeller, Acad. Sci. St. Louis, Trans., vol. 11, p. 16.3, pi. 14, figs. .3-4. 

 Kinderhook: Bed 4, Burlington, Iowa. 



This species is more abundant than s.ny other in the faunas from Colorado, 

 which I regard as of Mississippian age. It occurs in abundance in the San Juan, 

 Crested Butte, and Canyon regions, and amongst the impressions from Larimer 

 County, but it has not yet been identified at Leadville or at Perry Park. With some 

 exceptions the Colorado material possesses .somewhat coarser ribs than that from 

 Yellowstone Park or the specimens from Utah figured by White and by Hall and 

 Whitfield, but it agrees with perhaps the majoritj^ of typical representatives of the 

 species from the Cuyahoga shale of northern Ohio. The latter show a certain 

 amount of range in this particular, quite sufficient to embrace both foi'ms. 



The variety with coarse strias might pass without challenge for a form from the 

 Hermosa formation which I have identified as 8p. ioonensis. 



