GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 127 



convex, the ventral rather high and more or less contorted. The shell con- 

 tracts at the hinge, the area heing moderately high and strongly inclined back- 

 ward. The sculpture consists of fine, regular, subequal lirse (in one specimen 

 more or less distinctly alternating). In the type specimen the lira? are equal 

 over the median portion and separated by intervals slightly greater than their 

 own width. Here they occur ten in 5 mm. Toward the sides they are rather 

 more distantly spaced and are alternating. 



The rarity of this genus in our Pennsylvanian rocks constitutes an 

 a priori argument against these specimens belonging to Streptorhynchus. 

 On the other hand, it is difficult to understand how the process of fossili- 

 zation, while permitting the dental callosities to be preserved, could oblit- 

 erate all trace of the septum. 



Horizon and locality: Wewoka formation; Coalgate quadrangle, Okla. 



Chonetes granulifer var. armatus var. nov. 



The fossils included under this title occur associated with C. mcsolobus var. 

 decipiens, and with the more closely related C. granulifer. They are of small 

 size, 15 mm. being the maximum width observed, of moderate convexity where 

 not compressed, subquadrate shape, rather prominent beak, and faint though 

 distinct insinuation. About seven cardinal spines occur on each side of the 

 beak. 



The surface is marked by obsolescent lira? and by numerous small though 

 prominent spines. 



This variety is distinguished from C. granulifer by the smaller and 

 less projecting beak, the nearly obsolete liration, and the number and 

 prominence of the spines, although the latter character may be to some 

 extent the result of preservation. With the evidence at hand, however, 

 I would not feel justified in regarding these shells as true representatives 

 of C. granulifer. 



Horizon and locality: Wewoka formation; Coalgate quadrangle, Okla. 



Chonetes mesolobus var. decipiens var. nov. 



1899. Chonetes mesolobus. Girty, U. S. Geol. Survey. Nineteenth Ann. Kept, 

 pt. 3, p. 576. 

 Upper Coal Measures: Atoka quadrangle, Oklahoma. 

 1903. Chonetes mesolobus. Girty, U. S. Geol. Surw. Prof. Taper 16, p. 357, 

 pi. 1, figs. 20-23. 

 Hermosa formation : San Juan region, Colo. 

 Rico formation : San Juan region, Colo. 

 Maroon formation : Crested Butte district, Colo. 

 Carboniferous: Grand River region, Colo. 



This form differs from typical C. mesolobus in having a smooth instead of 

 striated surface. Though I was at first disposed to describe it as a new species 



