Bkkde.J Carboniferous Invertebrates. 93 



Ventral valve having its greatest convexity toward the beak ; 

 sides sloping away from the middle with a slight convexity and 

 becoming flattened or sometimes a little concave near the lateral 

 margins; beak rather small, prominent, and closely incurved 

 over that of the other valve ; mesial sinus very broad but not 

 deep, prolonged far upward at the front, becoming obsolete 

 about the middle of the valve and is entirely wanting upon its 

 posterior portion ; from two to four depressed, angular plica- 

 tions occupy the mesial sinus and disappear with it, the sides 

 and posterior portion being free from plications. Dorsal valve 

 more capacious than the ventral ; mesial fold distinct at the 

 front, and, like the mesial sinus, becoming obsolete about the 

 middle of the valve ; from three to five plications like those of 

 the other valve mark the fold, but the surface upon each side of 

 it is plain, like that of the posterior portions of both valves. 

 The whole surface marked by fine stria* of growth, but no radi- 

 ating stria* have been detected." Measurements of two speci- 

 mens : Length, 19 mm., 23mm.; width, 19 mm., 23 mm.; 

 convexity, 15 mm., 16 mm. 



Range and distribution: Lower Coal Measures; Coffeyville, 

 Montgomery county, Kansas City. 



Our specimens seem to agree very well with White's figures 

 and description, the principal difference being that the lateral 

 angles at the beak seem to be a little smaller. While there are 

 no radiating stria* in our specimens, the shell is very fibrous 

 and where exfoliated might appear to be striated. It differs 

 from P. pugnus missouriensis in having no plications on the 

 sides of the shell, and also in outline. 



Pugnax Utah. Plate XII, figs. 7-7c. 



Terebratula uta Marcou, Geol. N. Amer., p. 58, pi. vi, f. 12, (Feb. 1858). 

 Rhynchonella [Camarophorla i osagensis Swallow, Trans. St. L. Acad. 



Sci., i, p. 289, (June, 1858). 

 Rhynchoni lla "fa.li Meek and Havden, Proc. Acad. Nat. Sci. Phil., p. 27, 



(1&59): etc. 

 .' Rhynchonella species Salter, Quart. Jour. Geol. Soc, London, xvn, 



p. t'4, pi. iv, f. 5, (1861). 

 Camarophorla globulina Geinitz (non Phillips), Carb. u. Dyas in Neb., 



p. 38, pi. in, f. 5, (186C). 

 Rhynchonella osagensis Meek, Fin. K( j p. U. S. Geol. Surv. Neb., p. 179, 



pi. I, f. 9, pi. vi, f. 2, (1872 i ; etc. 



