CORRELATION OF CARBONIFEROUS ROCKS 353 



H., Myali?ia peratte?iuata M. & H., M. permiana (Swallow) M. & 

 H., Nautilus ecce?itricus M. & H., Nuculana bcllistriata Stevens var. 

 attenuata Meek, Pleurophorus Calhouni M. & H., P. subcostatus M. 

 & W., P. subcuneatus M. & H., Pscudomonotis Plawni (M. & H.) 

 sp., P. Hazv?ii (M. & H.) sp. var. ovata M. & H., Schizodus curtus 

 M. & W., 5. ovatus M. & H., and Yoldia substitute M. & H. 



All of the species are Lamellibranchs with the exception of 

 the Nautilus which is a Cephalopod. One species begins in the 

 Lower Coal Measures ; another is first reported from the Des 

 Moines of Iowa and then from the Kansas Permian, not appear- 

 ing in the interval ; six appear in the Upper Coal Measures and 

 the remaining six are known only in rocks of the age of Meek 

 and Hayden's Kansas Permian, with one exception, which is 

 reported from the Permo-Carboniferous of Utah and from rocks 

 in New Mexico referred doubtfully to the Upper Coal Measures. 



The abundant species and about the only ones found in the 

 upper part of the formation are : 



i. Bakevellia fiarva M. & H. — Permian of Kansas (in each instance 

 meaning that division of Meek and Hayden), and from Arizona in rocks 

 stated by Dr. White to probably belong in the Permian, while he found a 

 closely related form in New Mexico "at the summit of the Carboniferous 

 series" (U. S. Geog. Surv. W. ioo Merid., Vol. IV, p. 153). This species is 

 closely related to B. antiqua Miinster, which is common in the Permian of 

 England, Germany, and Russia. 



2. Myalina permiana (Swallow) M. & H. — Permian of Kansas and 

 Texas. Reported by Hall & Whitfield from the Permo-Carboniferous of 

 Utah ; and by Dr. White from New Mexico in rocks which were referred 

 doubtfully to the Upper Coal Measures. 



3. Pleurophorus subcuneatus M. & H. — Permian of Kansas; Dr. Keyes 

 reports: "There is but little doubt that the form from Des Moines [Lower 

 Coal Measure of Iowa] is identical with that figured by Geinitz in 1866 as 

 Pleiirophorus simplus of Keyserling" (Proc. Acad. Nat. Sci., Phil., 1891, p. 

 250) There is no other record, however, of the occurrence of this species 

 until Meek and Hayden's Permian is reached in Kansas, and Mr. Beede 

 informs me that he has not seen it below the Permian there. This species is 

 so nearly related to the P. simplus v. Keys. sp. of the Russian Permian that 

 Geinitz regarded them as identical. 



4. Pseudomonotis Hawni (M. & H.) sp. — Permian of Kansas. Heilprin 



