58 COLOHAltC) COLLEGE STUDIES. 



shoulder (the aiiijfulated suininit-line of the feeble keel made 

 by the apposed ed,u;es of the valves) a short distance from the 

 beaks; valves of quite moderate convexity; beaks placed a 

 little in advance of the middle, narrow, their tangent apices 

 curved inward and downward, but inclined forward in only a 

 very slight degree; anterior and posterior slopes more or less 

 flattened, the j)osterior separated from the discal slope, in the 

 cast, by a faint angulation; discal and anterior slopes orna- 

 mented with unequal concentric lines, and the posterior slope 

 with 35 or more radial raised lines, which are relatively much 

 finer than those of R. qmidrans. 



Measurements. — Height 78, length 69, breadth 50 mm. A 

 second specimen is relatively longer, measuring, height 71. 

 length 67, breadth 46 mm. 



Occurrence. — The types of this species are several casts, 

 two of which show the character of the ornamentation. They 

 were collected by Mrs. F. W. Cragin, Mr. J. T. Munson, and 

 the writer, chiefly from the Grayson marl, at the old D. B. 

 and N. O. railway cut about half a mile southeast of the Union 

 dejiot of Denison, Texas. A single example, somewhat smaller 

 than those from the marl, was obtained from the Main-street 

 limestone on the summit of the creek-bluff adjoining. 



Among the considerable number of fossils found associated 

 with the Roudairia denisonensis, are Exogyra nrietina, E. 

 drakei,Vo la texana,Avicula dispar. Sphenodiscus pedernalis, 

 Turriliies hrazosensis, etc. 



Pholadomya ragsdalei, sp. nov. 



Shell large, triangular-ovate, compressed, multicostate; 

 umbonal region somewhat elevated, but beaks not strongly 

 arched; much the larger part of the shell ornamented with 

 straight to slightly curved radial costse, which are narrow like 

 the intervals between them and more or less crossed and in- 

 terrupted by raised, concentric growth-lines; anterior area of 

 shell ornamented with a system of concentric, strongly curved, 

 loop-like to more or less nearly quarter-circlet costae which 

 are quite independent of the concentric, elevated growth-lines 

 and are severally continuous at their attenuated posterior 



