CA MBRIAN BRA CHIOPODA— WA L CO TT. 253 



NISUSIA (JAMESELLA) ERECTA, new species. 



General form transverselj semioval; hinge line a little shorter than 

 the greatest width; valves sabequally convex. Surface marked by 

 strong, broad, sharply rounded ril)s, three at the frontal margin in a 

 distance of 2 mm. ; the ribs appear to be simple and un))ifurcated from 

 the umbo to the margin, but owing to the small size of the shell this 

 statement may be modified by discovery of other specimens. 



Ventral valve convex; elevated at the umbo, apex worn by attrition, 

 but marginal. Area high, very slightl}' inclined backward; delthy- 

 rium large, triangular, length and width equal: deltidium convex, 

 imperforate, and nearly covering the delthyrium. Dorsal valve regu- 

 larly convex, most elevated at the umbo and curving over to the rather 

 low area. 



This species is distinguished by its strong, regular ribs and the 

 regular convexity of the dorsal valve. 



Fonnatio}! and locality. — Middle Cambrian. Limestone at the 

 south end of Timpapute Range, Groomc District, Nevada. 



NISUSIA (JAMESELLA) KUTHANI Pompeckj. 



Orthis kuthani Pompeckj, Jahrbuch k. k. Geol. Reichsanstalt, XLV, 1896, p. 514, 



pi. XV, figs. 8-13. 

 {Orthis romingeri Krejci, Novak, K. Feistmantel, Knsta, Katzer, Wentzel, Jahn. ) 



Original description. — Outline subrectangular, hinge edge straight with angles pro- 

 tracted but a short distance; length to breadth as 3 : 4, often less. 



Ventral valve highly arched. Apex drawn forward, but not curved toward the 

 dorsal valve at all, or in rare cases but slightly. Area high, steep, with sharp areal 

 edges and high, triangular foramen. Owing to the state of preservation, the details 

 of the inside of the valves can not be well observed. 



Dorsal valve flatter, with rather decided arching on side edge and frontal edge, with 

 sinus always distinct, which corresponds to a faint swelling at the frontal edge of the 

 ventral valve. The area is very low with a small triangular foramen. Crural proc- 

 esses narrow, considerably divergent. 



The surface is ornamented with narrow sharp ribs, increasing by interpolation. 

 The ribs are divided by interspaces which are considerably broader than the ribs. 

 In the interspaces there is frequently seen a lower, thread-like rib. The number of 

 ribs is 30 to 36. The ribs are mostly very distinct on the internal casts also. Some- 

 times internal casts are found which show remarkal)ly few ribs, and which in this 

 respect and also by their greater breadth approach Orthis perpasta var. macra. 



The present species has thus far been called, after Kusta's example, Orthis romin- 

 geri, but it differs from that species («) in the ventral valve, its apex never being so 

 strongly curved as in Orthis romingeri, and in most cases not curved at all; (h) in 

 the dorsal valve, which in the present species is more strongly arched with a more 

 decided sinus; (c) in the sculptiare, inasmuch as the ribs are narrower, sharper, 

 fewer in number, and separated by wider interspaces than in Orthis romingeri Barr. 



This species, eminently characteristic of the lower conglomerate zone of the 

 Kamenna hurka near Teji^ovic, was found in thousands of specimens (impressions 

 and internal casts) at the locality mentioned, in conglomerate-like, quartzitic sand- 

 stone and in the greywacke intercalations. I vsaw the species in similar rock from 

 Gross Lohovic southwest of Skrej. (Collection of the Bohemian University at 

 Prague. ) 



Proc. N. M. vol. xxviii — 04 17 



