FOSSILS OF THE HUDSON EIVER GROUP. 77 



above the middle of the Vcalve. Dorsal valve gibbous, subcircular ; the 

 beak extending a little above the hinge line, and the area extremely 

 short. Ventral valve broadly ovate, sloping from the beak ; beak pro- 

 duced bej'ond the line of the opposite valve, and pointed, not incurved ■ 

 area twice as long as high; foramen narrow and extending to the apex 

 of the beak, and sometimes truncating the extremity. 



Surface marked by from fifteen to twenty simple, abruptly rounded or 

 subangular plications. 



This small Orthis is so peculiar as not to be readily mistaken for any 

 other known in our strata. The short hinge line and area, and the pro- 

 duced beak of the ventral valve, are characteristic features. In some 

 specimens the area is obscure or undefined, and the shell has much the 

 aspect of Trematospira. It is a rare species, and I have not seen more 

 than twenty individuals, all of which preserve the characters given 

 above, the variation being mainly in the number of stria3 ; those Avith 

 fewer striae are frequently more gibbous than the others. Length about 

 one-third of an inch ; the width a little more. 



The above description is taken from the 13th Report of State Cabinet 

 of New York, 1858 and 1859. Up to the present time there are no new 

 facts in our possession in regard to the generic relations of this peculiar 

 shell. 



Formation and locality : In the calcareous shales of the Hudson Eiver group, near 

 Cincinnati, Ohio. From the collections of Mr. S. T. Carley and Mr. U. P. James. 



Oethis Jamesi. 



Plate 1, figs. 21, 22. 

 Orthis Jamesi, Hall; 1-lth Kept. State Cab., p. 89, 1S61. 

 Shell small, transversely semi-elliptical ; hinge line longer than the 

 width of the shell below, with somewhat salient angles. Valves convex, 

 the ventral much the deepest, with an elevated, almost pointed beak, and 

 rather high, vertical, or slightly overhanging cardinal area, which is 

 about four times as long as high, and divided in the center by a propor- 

 tionally large fissure, once and a half as high as wide ; the surface of the 

 valve is regularly and evenly sloping from the small pointed beak to the 

 edges of the shell in young specimens, and sometimes slightly carinate 

 on the umbo, or becoming broadly and shallowly sinuate in front in 

 larger individuals. Dorsal valve more evenly convex from the small 

 incurved beak to the front, when not distorted by compression ; often 

 depressed just within the cardinal angles, giving slightly recurring car- 



