THE LOWER EMBAR OF WYOMING 661 



sian Moscowian and in the Upper Pennsylvanian of the Mississippi 

 Valley, and Cladodus occidentalis in the Moscowian, the Embar, 

 and the Mississippi Valley Upper Pennsylvanian. 



Unfortunately the data for the fish remains from the Mississippi 

 Valley are not complete enough to furnish a basis for exact correla- 

 tion. The fossils are labeled, in most cases, as from the Coal 

 Measures, Upper Coal Measures, or Lower Coal Measures, and 

 the designations "Upper" and "Lower" are not trustworthy in all 

 cases. 



The data for the Russian specimens is not all that is to be 

 desired. Crassidonta stuckenbergi, with positive identification, is 

 from Samara, from beds correlated with the Moscowian by Stucken- 

 berg. Campodus corrugatus "appears to come from the Fusulina 

 limestone of Miatschkowa," the implication being that the speci- 

 men is not labeled. The identification of Cladodus occidentalism 

 is somewhat uncertain without comparison with American speci- 

 mens. 



ACKNO WLED GMENTS 



It is a pleasure to acknowledge the writer's obligations to Profes- 

 sor Stuart Weller for the loan of specimens and the privilege of 

 studying the fish remains in the Walker Museum of the University 

 of Chicago; to Dr. A. R. Crook for the loan of specimens from the 

 Illinois State Museum; to Dr. E. H. Barbour for the loan of speci- 

 mens from the University of Nebraska museum; to Dr. T. E. 

 Savage for the loan of material from the University of Illinois; 

 to Dr. Louis Hussakof for the loan of specimens from the American 

 Museum; and to Mr. D. K. Greger for assistance in preparing and 

 photographing the specimens. 



EXPLANATIONS OF PLATES 



PLATE I 



Figs. 1-5. — Helodus politus Newberry; co-types for comparison with the 

 figures of Helodus subpolitus (collection of the University of Chicago) . 



Figs. 6-16. — Helodus subpolitus n. sp.: Figs. 6-13, top views showing 

 variations; Figs. 14-16, side views showing crenulations (No. 704). 2 



1 Girty, Prof. Papers 58, p. 157. 



2 All specimens not otherwise designated are in the collection of the University 

 of Missouri, and the number given is the University of Missouri museum number. 



