BRACHIOPODA. 345 



elongate and narrow adductor. Within the anterior and lateral margins of 

 the valve is a thickened ridge which is crossed by branches of the vascular 

 sinuses. Brachial valve fiat in the umbonal region, very convex over the 

 median portion and sloping gradually to the margins. The cardinal process 

 consists of two slender and short apophyses which are united at their base 

 with the crural plates. The latter are very divergent and extend in a broad 

 curve subparallel to the hinge -line. The muscular scars consist of two pairs, 

 the posterior being broad and striated, the anterior narrow and close to the 

 median line. The members of the pairs are separated by a low median ridge. 

 Surfiice of the shell covered with numerous very fine filiform striae, regu- 

 larly but not conspicuously alternating in size. Delicate concentric striae are 

 sometimes discernible. 



Trenton horizon. Clifton and Janesville, Wisconsin. 

 This shell has been referred to the Hemipronites nutans, James (Meek), of 

 the Hudson River, group which it resembles in its general expression. It differs 

 from that species in its internal characters and more finely and abundantly 

 striated exterior. 



Orthothetes desideratus, sp. nov. 



PLATE IX A, FIGS. 26, 27. 

 1883. Streptorkynchus, sp. .» Hall. Kept. State Geologist N. Y. for 1882, pi. (xi a) 42, figs. 26, 27. 



The original specimens of this species are internal casts of a form with a sub- 

 circular marginal outline, very gibbous brachial valve which has its greatest 

 convexity central and slopes evenly to the margins, though with a slight 

 tendency to depression toward the cardinal extremities ; a strongly and reg- 

 ularly concave pedicle-valve, elevated at the beak and about the margins. 

 The cardinal area on this valve is moderately high and erect, the hinge-line 

 being slightly shorter than the greatest diameter of the valves. The sur- 

 face of both valves is covered with numerous fine radiating striae. The 

 general form and contour of the species is very similar to that of Orthothetes 

 umbraculum of the Eifel. 



Waverly group. Medina county, Ohio. 



