606 PROCEEDIXnS OF THE NATIONAL MUSEUM. vol. xxv. 



Through the courtesy of Dr. Brogger, I studied the material rep- 

 resenting this species collected in Norwa3\ 



In a collection kindly sent me by Dr. G. Lindstrom 1 find two 

 ventral valves from the black shale of Skane, ])ut it is in the collection 

 made by Mr. v. Schmalensee that specimens occur showing the casts 

 of the interior of the dorsal valve. These have the imprint of the 

 central visceral area; the large vascular sinuses, and the area. A cast 

 of an uncompressed shell proves that the visceral area was short and 

 relatively small. Comparing the matter, I am led to conclude that the 

 latter is a partially exfoliated specimen preserving the vascular mark- 

 ings on the thin inner lavers of the shell. 



In Cape Breton this species occurs abundantly in association with 

 Oholus {Lingulella) concinrms Matthew, and Acrotreta hlsecta Matthew. 

 The shells are all compressed in the shale, but a direct comparison of 

 the interiors of the valves of specimens from Cape Breton and from 

 the Ceratopyge shales of Sweden shows the two to be identical in all 

 characters except the length of the area and pedicle groove. The Cape 

 Breton shells have a longer area, but whether this is owing to the con- 

 ditions of preservation or not, I am unable to decide, as the material 

 from Sweden is very imperfect about the area. On one of the Cape 

 Breton shells the line punctse of the interior surface areclearlv shown. 



Formation and localities. — Upper Cambrian. Black shale 3 f, 

 Dictyograptus series; greenish arenaceous Ceratopyge shale 4a, Born- 

 holm. In dark, ferruginous sandstone, associated with fragments 

 of Olenus toimquisti Moberg, Skane Fagelsang, Sweden. Etage 3 

 aj. Vestfossum; Engervik, Asker; Slemmestad Roken, 3 ab, Kris- 

 tiania, Norway. Argillaceous shale, Barachois lln, 4 miles south 

 of Little Bras D'or Lake, Cape Breton, Nova Scotia. 



OBOLUS (LINGULELLA) LENS Matthew. 



Lingulaf lens Matthew, Bull. Nat. -Hist. 8oc. New Brunswick, IV, 1900, p. 274, 



pi. V, figs. 3a, 3b. 

 Obolus {Lingulella) belhis ^yALCOT^, Proc. U. S. Nat. Mus., XXIII, 1901, p. 685. 



General form broadly ovate. The ventral valve is subacuminate 

 and the dorsal valve very broadly ovate to subsemicircular. The con- 

 vexity of the valves is moderate, the ventral valve being most promi- 

 nent along the center, with the postero-lateral slopes somewhat 

 flattened toward the margin. 



Surface of the shell marked by line, concentric stride and lines of 

 growth, and the inner surface by concentric lines and ver}- fine radiat- 

 ing stria?. The shell is thinner than most species of the subgenus, 

 resembling in this respect Zing ula mur?x(yi &nd O. {L.)hellus. It is 

 formed of several lavers or lamelhe that are slightly oblique to the 

 outer la3"er. Dr. Matthew speaks of minute pits on the outer surface. 

 These also appear on the inner layers. I have been unable to deter- 



