42(i oaebonifekous formations and faunas of colorado. 



Myalina perniformis Cox? 



1857. Myalina pemaformi.i. Cox, Geol. Surv. Kentucky, vol. S, \t. 5()!i, |il. «, fig. 8. 

 Coal Measures: Providence, Hopkins County, Ky. 



At station 2187 was obtained a single specimen of Jfi/(////ii/ whicli I hiue refpncd 

 to Myalina jjernlf<n'mit<. Its somewhat crusiied condition prevents a satisfactorj' 

 reference. The shape and size, which gives a measurement of 31 mm. in the longest 

 diameter, arc almost preciseh^ those of M. pet'nifou'vvh as illustrated by Cox. 'riic 

 surface is largely exfoliated. The portions which remain, however, lead me to 

 believe that it did not have the strong concentric, almost fimbriating, lines of growth 

 described by Cox. My specimen is related also to M. apachesi and M. x^ffrattentrnta^ 

 l)ut it is nearest 31. perniformis. It also resembles the species which I have referred 

 to M. cuneiformis Gurley, but differs from it in having the umbonal ridge slightly 

 less oblique to the hinge line, and in having a somewhat more quadrate shape. 



Locality and liorison. — San Juan region (station 2187); Molas formation. 



POSIDONIELLA de Koninck. 1885. 

 Posidoniella pertenuis Beede? 



1895. Placunopsis carbon.aria. Keyes, Missouri Geol. Surv., vol. 5, p. 108, pi. 43, fig. 9 (date of 

 imprint 1894). 

 Upper Coal Measures: Kansas City, Mo. 



1899. Posidonomija peHenuis. Beede, Kansas Univ. Quart., vol. 8, p. 127, pi. 32, flg. 5. 



Coal Measures: From near the dam at Lawrence, Kans., and from the same stratum at Camerons 

 Bluff, 3 miles up the river. 



1900. Posklonomyaf pertenuis. Beede, Univ. Geol. Surv. Kansas, Kept., vol. 6, p. 136, pi. 19, fig. 5. 

 Upper Coal Measures: Lawrence, Kans. 



This form is represented by a single specimen obtained at station 2341 in the 

 Kico formation (Scotch Creek). Although not very perfectly preserved, the charac- 

 ters, made out as well as possible, would indicate that this specimen in its specific 

 relations is very close to that which Kej'es figures as Placunojisis carlionaria (see svn- 

 onymj'). Beede has called attention to the fact that this shell is quite unlike the form 

 to which Meek and Worthen gave the name P. carbonaria. Although the latter is 

 characteristically ornamented with radial markings, Meek and Worthen themselves 

 figure a shell as PI. carbonaria (their fig. 2b), which seems to be smooth, and which 

 has, moreover, much the shape of Keyes's specimen. It would appear verj^ much 

 as if Meek and Worthen's fig. 2b and possibly also their fig. 2d belonged to the 

 same species as the one figured hj Keyes, and that this type were distinct from P. 

 carbonaria. Beede also suggests that P. carbonaria of Keyes may belong to the 

 species which he describes as Posidonomyal pertenuis. P. perteiiuis is represented 

 by Beede' s figure as being a rather elongate form, and as Keyes's figure shows a 

 nearh* circular one the difference in shape is somewhat against this view. Never- 



