BRACHIOPODA. 341 



verse section across the umbo of one, shows that the dental lamellse, though 

 strong and convei'gent, did not unite to form a spondylium. Received from 

 Professor Safford. 



Trenton horizon (Glade limestone). Near Nashville, Tennessee. 



Orthis (Pl^siomys) loricula, sp. nov. 



PLATE Va, figs 32-34. 



Shell strophomenoid in outline ; reversed convex. Hinge-line long and straight 

 making the greatest diameter of the shell. Cardinal areas narrow, subequal. 

 In the pedicle-valve the delthyrium is covered by a convex plate extending 

 for one-half its length ; the area is erect, the beak not prominent. The 

 valve is slightly convex in the umbonal region but is depressed outward in 

 all directions, most strongly in the median line. The brachial valve is de- 

 pressed about the beak, convex over the pallial region and divided in the 

 median line by a shallow sinus. The interior characters of the valves are 

 essentially the same as those in Orthis subquadrata. 



External surface covered with numerous fine, elevated strias, alternating 

 in size and crossed by finer concentric lines. 



Length of an average specimen, 18 mm.; width, 21 mm. 



Trenton horizon. Fountain, Minnesota. 



Orthis (Dalmanella) arcuaria, sp. nov. 



PLATE Vc, FIGS. 20,21. 



Shell with a general similarity to that of Orthis elegantula, Dalman, but having 

 the marginal outline more circular, the pedicle-valve more evenly convex, 

 the umbo more prolate, and the brachial valve considerably more convex. 

 The pedicle-valve bears a broad fold, and the brachial a shallow sinus, in the 

 median line. In the interior of the pedicle-valve the muscular area is elon- 

 gate and very deeply impressed, the umbonal portion of this valve being 

 considerably thickened. 



