92 University Geological Survey of Kansas. 



a few very large, rounded or more or less angular, radiating 

 plications, which latter are never formed on the umbones, but 

 occupy the anterior half, and become more prominent toward 

 the front, where they often terminate in deeply interlocking 

 angular marginal projections. Of these plications there are two, 

 rarely three, on each side of the larger and more prominent one 

 forming the mesial fold on the dorsal valve, while on the ven- 

 tral valve there are three, rarely four, on each side of the mesial 

 sinus ; a few zigzag marks of growth also traverse the anterior 

 and lateral margins of the valves, parallel to their deeply 

 notched edges." The measurements of three specimens are 

 here given — one rather large, one medium, and one young speci- 

 men : Length, 23 mm., 16 mm., 8 mm.; width, 29 mm., 28 

 mm., 9 mm. ; convexity, 32 mm., 20 mm., 5 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Independence, Iola, Edwardsville, Eudora, Lawrence, Lecomp- 

 ton, Topeka. 



Besides the variation in size and age, this shell often pre- 

 sents very much the appearance of a Pugnax, which is caused 

 by the mesial plication being divided into two, and the presence 

 of a small fold to correspond in the mesial furrow of the other 

 valve. This gives the brachial valve quite a large mesial fold, 

 and a correspondingly large sinus in the pedicle valve. This is 

 hardly noticable in the majority of specimens, but in some it is 

 very marked. 



PUGNAX. 



Hall and Clarke, Pal. N. Y., VIII, pt. II, p. 202, ( 1893) ; Ann. Rep. N. Y. St. Geol., p. 208, for 1895. 



Pugnax rockymontana. Plate XII, figs. 8, 8b. 



Terebratula rockymontana Marcou, Geol. N. Amer., p. 59, pi. vi, f. 13, 



(1858). 

 Rhynchonella eatoniosfonnis McChesney, New Pal. Foss., p. 49, (1869). 

 Rhynconella rockymontana White, Wheeler's Expl. Surv. West 100 Mer., 



iv, p. 131, pi. ix, f. 1,(1875). 

 Pugnax eatoniiformis Hall and Clarke, Pal. N. Y., viii, pt. n, p. 204, 



(1893). 

 Pugnax rockymontana Schuchert, Bull. U. S. Geol. Surv. 87, p. 336, 



(1897). 



White's description: " Shell rather large, inflated, subtri- 

 hedral in outline, broadest near the front ; sides somewhat regu- 

 larly rounded from the anterolateral portions to the beaks. 



