488 ' GEOLOGY OF OHIO. 



MOLIyUSCOIDEA. 



BRACHIOPODA. 



Genus DISCINA Lamarck. 



Distinct, Meektsma Whit/. 



For references and synonym see page 483. 



Specimens of this species are not uncommon in both of these chert 

 • beds, the imprints only remaining. 



Genus SPIRIFERA Sowerby. 

 Spirifera {Martinid) lineata. ' 

 Plate XH, fig. 3-5. 

 Spirifera lineata Martin. 



Internal casts, of small size, of this, shell are quite common in the 

 upper chert layers of the Coal Measures in Hocking county, bearing all 

 the features of the species so far as the casts, are concerned, but the 

 matrix was not obtained in a sufficiently perfect condition to yield the 

 external form of the shell. In the black or lower cherts some of the in- 

 dividuals have, obtained a larger size, one specimen measuring about five- 

 eighths of an inch in transverse diameter. A small individual of the 

 species was obtained in the lower black chert, at Webb Summit, retaining 

 all the fimbriae of the surface in a most perfect manner, an enlarged figure 

 of which is given on Plate XII, fig 6. 



Genus ATHYRIS McCoy. 



Athyris subtilita. , 



Plate xii, figs. 7-9. 



Terebratula subtilita Hall, Stansbury's Rept. Great Salt Lake, 1852, p. 409, pi. iv (by 

 error in text pi. ii), fig. 1 a, b, and 2 a, b. Terebratula subtilita, Athyris subtilita, 

 and Spirigera subtilita of various authors. 



Internal casts of specimens of this species, of small size, are com- 

 mon in the upper chert beds of the Coal Measures in Hocking county, 

 Ohio. Individuals have been observed varying in size from less than one- 

 eighth of an inch to more then half an inch in diameter, but all in the 

 condition of casts. The larger specimens, although much smaller than 

 those usually found in the shaly limestones at Greentown and elsewhere, 

 nevertheless show distinctly by their markings and the distinctness of the 

 musculars scars that they' were adult shells, but probably stunted in 

 growth by Unfavorable conditions, as they are perfect in form and mark- 

 ings. The specimen illustrated on Plate XII, figs. 7-9, is from the cherty 

 layers at Mrs. Banks, in the railroad cutting, Falls township. The indi- 

 viduals from the black cherts, at Webb Summit, Hocking county, are of 

 larger size, and correspond more nearly with the ordinary forms of the 

 species. 



