220 THOMAS H. CLARK 



Our specimens are all of a gently undulating, flattened form, 

 but much of the structure has been destroyed by weathering. This 

 condition is not confined to the surface, for much of the internal 

 structure of the fossil is now indistinct. Beyond a rugosity devel- 

 oped somewhat concentrically within a slightly upturned margin, 

 there are no surface markings of distinctive value. The best natural 

 section of the skeleton shows very fine corrugations spaced 4I per 

 millimeter. These appear upon a poHshed surface as lines of black 

 dots crossing the white calcite. It may be that these dots represent 

 the junction of radial pillars with the laminae, but neither pillars 

 nor laminae have been preserved. The same structure is expressed 

 on weathered edges by extremely fine ridges. Under these cir- 

 cumstances, specific identification is impossible, and even generic 

 determination is largely a matter of conjecture. Our specimens are 

 from 10 to 24 mm. thick, and the largest fragment is 34 cm. across. 

 This was broken from a whole specimen which was more than 2 

 feet across. 



BRYOZOA 



Three or four species occur in the collection, but I have not 

 attempted their identification. They are for the most part 

 Fenestellids. 



BRACHIOPODA 



Stropheodonta sp. 



The interior of a pedicle valve of a species belonging to this 

 genus is present in our collection. It has no characteristics of 

 specific import. 

 A try pa reticularis (Linne) 



Abundant. Our specimens vary in form from those in which 

 the valves are equally convex to those in which the pedicle valve is 

 almost flat. They are all rather small, seldom attaining a width 

 or a length of 20 cm. 

 Spirifer lucasensis Stauffer^ 



Much more abundant than Atrypa reticularis. Our specimens 

 are identical with those from Ohio, save that in some the hinge 

 line is a little less than the greatest width of the valves. Inasmuch 



' C. R. Stauffer, Geol. Surv. Ohio., Bull. 10 (1909) fourth series, pp. 188-89, PI- 16, 

 Figs. 1-5. 



