DESCRIPTIONS OF SPECIES. 449 



the tip of the umbone, and sloping- downward gradually merges with the strong- 

 posterior curvature. The most elevated portion of the shell is central. It is bounded 

 by two indistinct diverging lines, which have their origin at the umbone. From this 

 area the curvature is rapid in its descent upon either side. 



The surface is marked by strong, regular, concentric ridges, which ai-e crenulate 

 or denticulate over the body of the shell, but laterallj^ the crenulations increase in 

 prominence until they become continuous radiating ribs, and dominate the concentric 

 markings of which they are elsewhere a subordinate feature. 



The ornamentation and configuration of this shell taken together are unlike any 

 Carboniferous genus with which I am acquainted. It is to be regretted that none of 

 the hinge characters could be ascertained so as to determinate its generic position, 

 and it is possible that better preserved material than that before me may lead to the 

 modification even of the description which I have thus far been able to draw up. 



Locality and horizon. — San Juan region (station 2219); upper portion of the 

 Hermosa formation. 



CYPRICARDINIA Lamarck, 1801. 

 Ctpricardinia caebonaria Meek. 



1871. Cypricardiniaf carhonarla. Meek, Acad. Nat. Sci. Philadelphia, Proc, p. 163. 



Lower Coal Measures: Newark, Ohio. 

 1875. Cyprk-ardmiu? carbonarhi. Meek, Pal. Ohio, vol. 2, p. 342, pi. 19, figs. 8a, b. 



Lower Coal Measures: Newark, Ohio. 

 1887. Ci/pricardinia (f) earbonarin. Merrick, Sci. Lab. Denison Univ., Bull., vol. 2, p. 35, pi. 4, figs. 

 17, 18. 



Coal Measures: Flint Ridge, Ohio. 

 1895. Pleurophorus oblongun. Keyes, Missouri Geol. Surv., vol. 5, j). 125, pi. 46, fig. 8. (Date of 

 imprint 1894.) 



Upper Coal Measures: Kansas City, Mo. 

 1900. Cypricardiniaf earbonarin. Beede, Univ. Geol. Surv. Kansas, Kept., vol. 6, p. 164, pi. 20, fig. 16. 



Upper Coal Measures: In the Oolite at Eosedale and Turner, Kans. 



There are a few specimens from istation 2219 south of Marguerite Draw in the 

 San Juan which probably belong to Meek's species cited above. They also closely 

 resemble the Waverlj^ form Gypricardinia scitula of Herrick. If one can rely upon 

 his figures, the specimen represented by fig. S of pi. 46, which Keyes identifies as 

 Plenn'oplioriix obloiiguti is a member of the genus Cypricardinia and possibly a 

 representative of the species under discussion. It almost cei'tainly is incorrectly 

 identified as PI. oljlongus. 



Locality and horison. — San Juan i-egion (station 2219); upper portion of the 

 Hermosa formation. 



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