736 CAMBRIAN BEACHIOPODA. 



indistinct area, with a low, broadly triangular foramen. On the frontal margin a strong, broad swelling of the edge 

 of the valve corresponds to the sinus of the ventral valve. 



Judging by some internal casts and impressions, the shell is ornamented with some 40 broad ribs, of which about 

 half are inserted between the primary ribs at various distances from the apex. Concentric lines of growth cross the 

 ribs. On the top of the shells, along some of these lines of growth (1 or 2) the sections of the shell are found to be 

 imbricated; near the frontal edge such imbrication is present more frequently in very short intervals. 



Orthis perpasta differs from Orthis huthani in its greater breadth, in the almost uniform and much stronger arching 

 of both valves, and also in the fact that in the former species the ventral valve bears a sinus, whereas in Orthis huthani 

 the sinus is on the dorsal valve. 



Observations. — Doctor Pompeckj very kindly sent me several fragments of sandstone con- 

 taining casts of the interior and exterior of the valves. The specimens illustrated by Pompeckj 

 [1896b, PI. X"\\l are smoother than most of those sent to me, but the description corresponds to 

 the ribbed specimens and a few nearly smooth interior casts occur m association with the more 

 strongly ribbed shells. The convexity of the ventral valve is quite variable, but is usually 

 considerable. One of the marked characters of the dorsal valve is the large transverse space 

 (pseudocrurahum) inside the valve beneath the umbo. In one example it is crossed vertically 

 by the main vascular sinuses. What may be a trace of a low, simple, rounded cardinal process is 

 shown in one cast. The crura were strong, with small dental sockets beside them. 



Nisusia (JameseJla) perpasta resembles Nisusia alberta (Walcott) in form and convexity, 

 but it does not have a spinose surface. 



Formation and locality. « — Lower Cambrian: Conglomeratic sandstones and graywacke inclusions in the lower 

 conglomerate zone of the KamennA hurka at the following localities [Pompeckj, 1896b, p. 516]: (345i) near Tejfovih; 

 and (345j) at Gross Lohovic, southwest of Skrej; both in Bohemia, Austria-Hungary. 



(345k) Sandstones at Slapnicky mlyn, near Skrej, Bohemia, Austria-Hungary. 



Nisusia (Jamesella) perpasta macea (Pompeckj). 



Plate CI, figures 3, 3a. 



Orthis perpasta macra Pompeckj, 1896, Jahrb. K.-k. geol. Reichsanstalt, Bd. 45, p. 516, PI. XV, fig. 14. (Charac- 

 terized in German as a new variety; see below for translation. Fig. 14 is copied in this monograph, PI. CI, 

 fig. 3a.) 



Nisusia (Jamesella) perpasta macra Pompeckj, Walcott, 1905, Proc. TJ. S. Nat. Mus., vol. 28, p. 255. (Original char- 

 acterization copied and variety discussed as below.) 



The original description by Pompeckj follows: 



Some internal casts and impressions of dorsal valves agree in outline perfectly with the dorsal valves of Orthis 

 perpasta, but differ from the type form by much less arching and ribs farther apart. 



Observations. — The gradual increase in the width of the interspaces between the ribs, from 

 a very narrow space to several times the width of the rib, makes this variety of doubtful value. 



FoEMATioN AND LOCALITY. — Lowcr Cambrian: Conglomeratic, quartzitic sandstones and graywacke inclusions 

 in the zone of the KamennA hurka at the following localities [Pompeckj, 1896b, p. 516]: (3451) near Tejfovih; and (345j) 

 at Gross Lohovic, southwest of Skrej; both in Bohemia, Austria-Hungary. 



Nisusia (Jamesella) perpasta subquadrata (Pompeckj). 

 Plate CI, figures 2, 2a-b. 



Orthis perpasta subquadrata Pompeckj, 1896, Jahrb. K.-k. geol. Reichsanstalt, Bd. 45, p. 516, PI. XV, figs. 19 and'20. 



(Described and discussed in German as a new variety; see below for translation. Figs. 19a and 20a are copied 



in this monograph, PL CI, figs. 2a and 2b, respectively.) 

 Nisusia (Jamesella) perpasta subquadrata Pompeckj, Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 255. (Original 



description copied, and variety discussed as on p. 737.) 



The original description by Pompeckj follows: 



As compared with the type form, this variety is distinguished by less breadth, the length being to the breadth 

 as 3 to 4. The anterior angles of the straight hinge edge are drawn in somewhat more than those of Orthis perpasta. 

 The ventral valve is higher, with higher and steep area, pierced by a large triangular foramen. The sinus, which 



o Localities 345i and 345k are represented in the oollections of the United States National Museum. 



