BRACHIOPODA. 139 



The surface is marked by numerous closely arranged slender subequal striae, which 

 are bifurcated or increased by intercalation, and are continued on the cardinal ex- 

 tremities to within a little distance of the hinge line; beyond which, the surface is marked 

 by lamellose concentric striae. In well-preserved surfaces, the radiating striae are 

 crossed by undulating concentric striae; but in the greater number of specimens, these 

 are not preserved, and the radiating striae have a fibrous appearance." 



Remarks — This is one of the most abundant forms in the St. Laurent limestone. 

 In the sandstone phase the specimens are preserved as internal moulds and in the 

 limestone usually as exteriors. The specimens from the sandstone are larger than from 

 the limestone. Spines along the hinge line are only rarely preserved. 



Chonetes mucronatus (Hall) 

 Plate 35, figures 13 and 14 



1843. Strophomena mucronata Hall, Geol. New York, Rep. Fourth Dist., p. 181, fig. 



3, on page 180. 

 1857. Chonetes laticosta Hall, Tenth Rep. New York State Cab. Nat. Hist., p. 119. 

 1867. Chonetes mucronata Hall, Pal. New York, IV, pp. 124-126, pi. 20, figs. 1, 2; 



pi. 21, fig. 1. 

 1897. Chonetes mucronatus Schuchert, Bull. U. S. Geol. Surv,, 87, p. 176. 

 1901. Chonetes mucronatus Kindle, Indiana Dept. Geol. Nat. Res., 25th Ann. Rep., 



p. 606, pi. 4, fig. 11. 

 1909. Chonetes mucronatus Grabau and Shimer, North American Index" Fossils, I, p. 



235, fig. 286. 



1912. Chonetes mucronatus Kindle, Bull. U. S. Geol. Surv., 508, p. 71, pi. 3, figs. 13, 14. 



1913. Chonetes mucronatus Prosser and Kindle, Maryland Geol. Surv., Middle and 

 Upper Devonian, pp. 146-148, pi. 11, figs. 11-17. 



Hall's description — "Shell small, semioval, moderately convex, nearly flat (often 

 flattened in the shale and gibbous in the limestone); cardinal line equalling or a little 

 greater than the width of the shell below; the extremities sometimes salient. 



The dorsal valve is very moderately concave or nearly flat. 



The surface is marked by twenty to twenty-four or twenty-six nearly simple sub- 

 angular striae, which are not so wide as the spaces between them. Sometimes one, two 

 or three of these striae are bifurcated towards the margin. The radiating striae are 

 crossed by extremely fine concentric elevated striae. 



The cardinal margin shows two and rarely three spines on each side of the centre 

 which are abruptly bent outwards so as to lie nearly parallel to the hinge line, and the 

 outer one extending much beyond the cardinal extremity. The area is very narrow." 



Remarks — This species is abundant in the Grand Tower limestone of Little Saline 

 Creek and common in the St. Laurent sandstone, \ x /2 miles west of Lithium, Perry 

 County. 



Chonetes scitulus Hall 



Plate 32. figures 8 and 9 



1857. Chonetes scitula Hall, Tenth Rep. New York State Cab. Nat. Hist., p. 147. 

 1867. Chonetes scitula Hall, Pal. New York, IV, pp. 130-131, pi. 21, fig. 4. 

 1897. Chonetes scitulus Schuchert, Bull. U. S. Geol. Surv., 87, p. 178. 

 1909. Chonetes scitulus Grabau and Shimer, North American Index Fossils, I, p. 237, 

 fig. 289, a-b. 



1912. Chonetes scitulus Prosser, Geol. Surv. Ohio, series 4, Bull. 15, pp. 541-542, pi. 

 32, fig. 6. 



1913. Chonetes scitulus Prosser and Kindle, Maryland Geol. Surv., Middle and Upper 

 Devonian, pp. 150-152, pi. 12, figs. 1-8; pi. 50, figs. 11-13. 



