598 



CAMBRIAN BRACHIOPODA. 



middle of the valve. No clearly defined muscle scars are shown on any of the specimens. 

 Casts of the interior of the dorsal va,lve give little satisfactory data in relation to the muscle 

 scars. The cast illustrated bj" Plate LV, figure 3e, shows a part of the outline of the visceral 

 area, also the impression of the transmedian muscle scar. 



Observations. — This species has been considered as the European representative of 0. 

 crassa (Hall), which occurs at the same relative stratigraphic horizon at Troy, New York. 

 The Swedish form differs specifically from the American in having a slightly more elongate 

 pedicle tube and in having the interior thickenings of the area more strongly developed. It 

 differs from 0. atlantica Walcott and 0. chromatica Billings in having a much more robust shell 

 and in many slight details. 



Kjerulf [1873, p. 83, figs. 10 and 11] illustrates, without text reference, a form that appears 

 to be referable to this species. It is found in Locality 324, at Tomten, Norway, in association 



with Holmia Jcjerulfi, Arionellus, 



and Oholella (Glyptias) favosa. 



The specific name was given 

 in honor of Dr. J. C. Moberg. 



Formation and locality. — Lowei 

 Cambrian : (331v) Gray sandstone of the 

 Mesonacis torelli zone at Bjorkelunda, 

 south of Simrishamn, Province of Chria- 

 tianstad; and (321s) brown sandstone in- 

 terbedded in gray sandstone at Sularp, 

 near Lund, Province of Malmohus; both 

 in Sweden. 



(8v) Shales and dark, calcareous, 

 ferruginous rock in the upper portion 

 of the Holmia Ijerulfi zone, Ringsaker; 

 and (324 [Kjerulf, 1873, pp. 73 and 88]) 

 green shales with interbedded calcare- 

 ous sandstone at Tomten, in Ringsaker; 

 both in the Province of Hedemarken, 

 Norway. 



FiGUBE 53. — Oholella vermilionenfsis n. sp. A, Cast of the interior of a Tentral valve, the type 

 specimen (X 2), from Locality 60b, Lower Cambrian sandstones in Vermilion Pass.Alherta, 

 Canada (U. S. Nat. Mus. Cat. No. 66600a). B, B', Top and back views of a dorsal valve 

 associated with the specimen represented in figure 53A (X 2) (U. S. Nat. Mus. Cat. No. 

 56606b). C, Ventral valve preserving its shape but from which all traces of shell sub- 

 stance have been removed (X 2). It is associated mth the specimens represented by 

 figures 53A and 53B (U. R. Nat. Mus. Cat. No. 5660Cc). D, Ventral valve from Locality 

 14p, Lower Cambrian sandstones near Resting Springs, California (U. S. Nat. Mus. Cat. 

 No. 51964a). E, Associated dorsal valve, Locality 14p ( U. S. Nat. Mus. Cat. No. Sigs-lb). 



Obolella vermilionensis n. sp. 



, Text figures 53A-E. 



This species is represented 

 bj^ numerous casts in a fine- 

 grained sandstone. General form 

 Shells fairly convex and viniformly larger than those of the 



suborbicular, slightly transverse 

 other species of the genus. 



The beak of the ventral valve is somewhat lower than the greatest elevation of the shell, 

 and does not reach the posterior margin. Both the beak and the area are, as a rule, poorly pre- 

 served, but the incurving of the growth lines to form the area is well shown in several specimens. 

 Interior casts of the ventral valve show traces of vascular sinuses. 



The beak of the dorsal valve terminates at the posterior margin, but is raised slightly 

 above the plane of the margin of the shell. 



Shell substance not preserved, but the casts show indications of both radial and concentric 

 striation. 



Observations. — The representatives of this species occur in such widely separated parts of 

 the Rocky Mountain province as California and British Columbia, but the forms are identical 

 and are associated in each district with Holmia and OrtTiotlieca. 



Obolella crassa approaches this species in the size of some of its specimens, but it is uni- 

 formly smaller and less convex. Obolella vermilionensis also differs from the former species in 

 its transverse outline. Further comparison is impossible because of the lack of knowledge as 

 to the interior of Obolella vermilionensis. 



