430 CABHONIFKROITS FORMATIONS AND FAUNAS OF OOI-ORADO. 



may be taken as evidence that this is not the case. They seem to he ([iiite distinct 

 from any American species yet described. 



Locality aiicf horison. — San Juan region (stations 2341, 2344, 2345); Rico for- 

 mation. 



MONOPTERIA Meek and Worthen, 1866. 



MoNOPTERiA POLiTA White. 



18S(t. Aiitliracopteru pulila. White, U. S. Geol. Geog. Surv. Terr., Twelfth Ann. Kept., for 1878, pt. 1, 

 p. 166, pi. 41', figs. 5a, b. 



Coal Measures: Major's Mill, Vermilion Coanty, 111. 

 1895. Monopteria sp. Keyes, Missouri Geol. Surv., vol. 5, pi. 46, flg. 10. (Date of iiuiirint, 1894.) 



Upper Coal Measures. 



I have long harbored a belief, to which I now venture to give expression, that 

 Anthracoptera polita White properly belongs to the genus Monopteria. The recent 

 exposition of Naiadites (= Anthracoptera), which we owe to Dr. Wheelton Hind," 

 makes it highly probable that a shell with the configuration shown by W^hite's figures 

 does not belong in Dawson's genus, and in the same characters this fossil strongW 

 suggests the genus to which it is now referred. This resemblance and the associa- 

 tions which arise from it have received some expression in geologic literature. I 

 have no doubt that the shell figured by Keyes as Monopteria sp. is a representative 

 of Anthracoptera polita, and Beede and Rogers practically suggest a generic relation- 

 ship when describing Monopteria f subalata by comparing their form with White's 

 species. The former, it ma}^ be remarked, seems to be correctl}^ referred to Monoj)- 

 teria if one may judge by its shape and bj' the other characters noted bj^ its authors, 

 but I would suggest that it is possibly founded upon young specimens of M. longi- 

 spina. The growth lines in that form indicate that the auricle is comparatively 

 undeveloped in its younger stages, taking on the alate condition gradually on advanc- 

 ing to maturity'. Immature shells of M. lonrjispina as outlined by growth lines on 

 larger individuals have exactly the shapes of the tj^pes of M. suhalata. 



1 have identified Monopteria polita in the Rico formation, where it is associated 

 with another shell believed to represent M. alata Beede. The relationship of these 

 species appears to be so close, however, that they should hardly be regarded as more 

 than varietally distinct. At the same time I would be unwilling for the present to 

 admit that they were specifically the same. 



Locality and horizon. — San Juan region (station 2342); Rico formation. 



Monopteria longispina Cox. 



1857. Gervilla longispina. Cox, Geol. Surv. Kentucky, vol. 3, p. 568, pi. 8, fig. 6. 

 Coal Measures: Providence, Hopkins County, Ky. 



«Mon. on Carbonicola, Anthracomya. and Naiadites; Paleontograph. Soc, 1894-1896. 



