58 BRACHIOPODS. 



Orthis emacerata HALL. 



Orthis emacerata Hall, 1860: 13th Reg. Rep. St. Cab. New York, p. 12U 

 Orthis emacerata Hall, 1862: 15th Reg. Rep. St. Cab. New York, pi. ii, 



figs. 1-2. 

 Orthis emacerata Meek, 1873: Geol. Sur. Ohio, Pal., vol. I, p. 109, pi. 



viii, figs, la-d and 2a-g. 



Shell small, plano-convex, rather depressed, transversely 

 truncato-suboval, the length being about five-sixths its breadth; 

 hinge-line perhaps always a little shorter than the greatest 

 breadth of the valves; lateral margins generally rounding to 

 the hinge, most prominent at or a little behind the middle, and 

 rounding to the front, which is usually somewhat straightened,. 

 or very faintly sinuous, at the middle ; or presents a regular 

 semicircular outline. Dorsal valve nearly flat, or slightly con- 

 vex on each side of a shallow mesial sinus, that commences 

 very narrow at the beak, and usually widens rather rapidly to 

 the front ; beak very small, scarcely projecting beyond the 

 edge of the area, and not incurved ; area low at the middle, 

 and narrowing off to nothing at the lateral extremities of the 

 hinge, slightly arched, and directed obliquely backward ; fore- 

 arm very small and filled by the cardinal process. Interior 

 very shallow, and provided with a slender mesial ridge that 

 extends about half way forward from the hinge, between the 

 muscular impressions, which are not usually well denned; 

 scars of posterior pair of adductor muscles smaller, and 

 usually deeper, than the interior, and situated close back under 

 the brachial processes; those of the anterior pair three or 

 four times the size of the posterior, sub-oval in form, and 

 extending to near the middle of the valve; cardinal process 

 very small and trifid ; brachial processes comparatively rather 

 stout and prominent; internal surface having the radiating 

 striae of the exterior rather distinctly impressed through as it 

 were, in consequence of the thinness of the shell, and finely 

 granular, the granules being apparently connected with the 

 punctate structure of the shell. 



Ventral valve compressed, convex, the greatest convexity 

 being near or a little behind the middle, along a more or less 



