440 CARBONIE'EKOUS FORMATIONS AND FAUNAS OF COLORADO. 



said to be " compressed," meaning, it is inferred, not very convex. My Colorado 

 specimens, liowever, are strongly arclied and show more modeling about the anterior 

 portion than is seen in Meek's figure, the umboncs being well defined. These shells 

 also resemble Scldzodm ovattta, but aside from being very much larger they have the 

 umbones less central than that species. 



Locality and honzon. — San Juan region (stations 23-iO, 2341, 2342); Rico forma- 



tion. 



ScHizoDUS MEEKANUS Girty. 



1871. Schizodus wheelerl (pars). Meek, U. S. Geol. Surv. Nebraska, p. 209, pi. 10, figs, la, b, c, d (and 

 le, If?). 

 Upper Coal Measures: Adams and Union counties, Iowa. 

 189-1. Schizodus whederi (pars). Keyes, Missouri Geol. Surv., vol. 5, p. 123, pi. 46, figs. 3a, b. 



Upper Carboniferous (Upper Coal Measures): Kansas City, Mo. 

 1899. Schizodus meek-anus. Girty, U. S. Geol. Surv., Nineteenth Ann. Rept., pt. 3, p. 583, pi. 72, figs. 

 7a-7c. 

 Upper Coal Measures: Atoka quadrangle. 



One large elongate specimen from station 2337, in the San Juan region, agrees 

 closely with the types of this species. The identification is made with some confidence. 

 Locality and horizon. — San Juan region (station 2337); Rico formation. 



Schizodus pakdattjs Girty? 



1899. Schizodus pandalus. Girty, U. S. Geol. Surv., Nineteenth Ann. Kept., pt. 3, p. 583, pi. 72, fig. 5a. 

 Upper Coal Measures: McAlester quadrangle. 



In the red calcareous sandstones of the Rico formation, from which collections 

 were made at stations 2340, 2346, and 2348, shells belonging to the genus Schizodus 

 are extremely abundant. The preservation is unfortunately so poor that I am unable 

 to ascertain definitely whether one or a larger number of species are present. 

 Some of the more perfect specimens, however, seem to have the shape of Schizodus 

 pandatus^ and to that species I have referred the whole collection, except a few speci- 

 mens from station 2340, identified as Schizodnxs cuneatus. In fact, it may be said of 

 the whole representation of Schizodus that the shells are too poorlj'^ preserved or too 

 fragmentary to permit of wholly satisfactory identification. 



Locality and horizon.— ^a.n Juan region (stations 2340, 2346, 2346, 2348); Rico 

 formation. 



Schizodus sp. 



At station 2205, on the west side of the Animas Valley, in the San Juan region, 

 a single specimen of Schizodus was obtained. Both valves are preserved, but both 

 are more or less crushed, and the original shape can onlj' be ascertained by a process 

 of estimation. It is one of the suborbicular types with, however, a well-marked 



