408 CMIBRIAN BRACHIOPODA. 



Obolus panderi Mickwitz. 



Obolm panderi Mickwitz, 1896, M^m. Acad. imp. sci. St.-P6tersbourg, 8th ser., vol. 4, No. 2, pp. 149-151, PI. II, 

 figs. 13a-d. (Described and discussed in German as a new species.) 



According to Mickwitz, two fragments of this species have been found. These fragments 

 indicate that the shell was one of the largest species from the Obolus sandstone, being nearly 

 twice as large as the nearly related 0. triangularis Mickwitz. He separates it from the latter 

 species on account of its size, "the pronounced pentagonal angular central groove, and the 

 remarkable combination of the corneous projection with the ridges of the main vascular canals, 

 and the somewhat less convexity of the ventral valve." 



Mickwitz states that this species is very rare. He gives a most detailed account of it, 

 to which the student is referred. 



The specific name was given in honor of C. H. Pander. 



Formation and locality. — Tipper Cambrian: (396 [Mickwitz, 1896, p. 151]) Obolus sandstone at Joa, near Jege- 

 lecht, 12 miles (19.3 km.) east of Reval, Government of Esthonia, Russia. 



Obolus parvus Walcott. 

 Text figures 37A-B. 



Obolm parvus Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 61-62, PI. VII, figs. 10 and 10a. (Described 

 and discussed as a new species. Figs. 10 and 10a are copied in this monograph as figs. 37A and 37B.) 



Shell small, moderately convex, nearly semicircular in outline. Ventral valve a little 



longer than wide and with the umbo curving gently to the minute marginal beak. Dorsal 



valve a little wider than long and with apex marginal. Sxu-face marked 



jf^^ ^gf^l^ by minute concentric strife of growth and an exceedingly fine network 



njj^B IgHJ^H of irregular lines that, with a lens magnifying 20 diameters, give it the 



^^^T ^^^^i appearance of the surface of Lingulella (Lingulepis) longinervis (Mat- 



A B thew) (PI. XLIV, fig. Ip). Nothing is known of the interior of the valves. 



Figure 37.-06of!is parMs wai- The average diameter of the valves is from 1.5 to 2 mm., with the 



cott. A, exterior of a ventral yeutral valve a little longer than wide and the dorsal valve slightly trans- 



valve, ttietypespecimen(U. S. ... o ^ 



Nat. Mus. Cat. No. 51400a). B, vcrse m Outline. 



exterior of a dorsal valve (U.S. jj^ outline the shell approaches most nearly to-Obolus rotundatus 



Nat. Mus. Cat. No. 51400b). ^_^ , ^ ,_,, ^^,^ _ „ „ s o ,i -«,-iii i tt /~, i • 



Figures 37A and 37B are copied (Walcott) (PI. XX, figs. 2, 2a-e) of the Middle and Upper Cambrian. 

 from Walcott [igosd, PI. VII, flgs. It differs in having a more rounded posterior outline in the ventral valve 

 ZTZX^^ZZZZ and in its more transverse dorsal valve. _ Obolus pheres Walcott (PL XI, 

 brian shale, on Mount Bosworth, figs. 6, 6a-b) of the Upper Cambrian is a very small shell, but it is 

 British Columbia. thicker and also more elongate than 0. parvus. In form it resembles 



Obolus minimus Walcott, from China (PI. XI, figs. 8 and 8a), but it differs in having a less elon- 

 gate ventral valve and in its peculiar surface. 



Formation and locality. — Lower Cambrian: (35c) Drift blocks of siliceous shale supposed to have come from the 

 Mount Whyte formation [Walcott, 190Sf, p. S14], found on the south slope of Mount Bosworth, about SOO feet {152 m.) 

 northwest of the Canadian Pacific Railway trach between Stephen and Hector, eastern British Columbia. 



(35e) About 270 feet (82.3 m.) below the Middle Cambrian, in a greenish siliceous shale correlated with No. 3 of 

 the Mount Whyte formation on Mount Bosworth. [Walcott, 19081, p. 214], in the amphitheater between Popes Peak 

 and Mount Whyte, about 3 miles (4.8 km.) northwest of Lake Louise, southwest of Laggan, on the Canadian Pacific 

 Railway; and (58t) sandy shale about 150 feet (45.7 m.) below the Middle Cambrian, just below the big cliff on the 

 east shoulder of Castle Mountain, north of the Canadian Pacific Railway; both in Alberta, Canada. 



Obolus pheres Walcott. 

 Plate XI, figures 6, 6a-b. 

 Obolus pheres Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 328. (Characterized as below as a new species.) 



This is one of the smallest of the Obolus species known to me, as it does not average 2 mm. 

 in diameter. It recalls at first sight Lingulella vnnona convexa (Walcott) ; but it differs in having 

 a thick lamellated shell and in being more rounded on the cardinal angles. The exterior 



