276 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



To it eorre.spoiiclH on Mie doi>;al valve a well-marked .sinus, limited on each side by a 

 strong bundle of ribs. 



The form just described agrees in the main so well with the tigures given by Salter 

 and Davidson of the small English form identified with Wahlenberg's lenticularis, 

 that I can hardly doubt its specific identity with the latter. 



Of Orthls sp, he remarks: 



Before me lies a cast from Tilcuya, representing a third Orthis species. It is almost 

 equal in size to 0. saUensis, but differs from it by its outline, which is greatly pro- 

 longed transversely, the greatest breadth at the hinge edge, and the feebly wing-like 

 projection of the hinge corners. This last-named characteristic and the much larger 

 dimensions distinguish this fossil also from 0. lenticularis. The surface of the shell 

 has been covered with very strong bundles of ribs. 



Formation and localities. — Upper Cambrian. Olenus schists, Nuniie- 

 burg; Olands; alum shales, Andrarum; many localities in West Got- 

 land, Sweden. 



In Norway Doctor Brogger describes it from Vestfossen in associa- 

 tion with Peltura scarahseoides. 



In Wales it occurs at the following localities, according to Davidson.'* 



Orthis lenticularis seems to be confined to the LTpper Lingulaflags (Dolgelly groups 

 of Belt, or upper portion of the Ffestiniog group of Sedgwick), and occurs at Pen- 

 morfa Church, near Tremadoc; near Criccieth, at Ogof-ddn Cliff, Swerny-y-Barcud, 

 Rhiwfelyn, and in several other Welsh localities. '■ 



In New Brunswick Dr. G. F. Matthew states that it occurs in great 

 numbers and all sizes in limestone lentiles, inclosed in the black shale 

 of division 3a, at Germaine street, St. John. 



In Newfoundland I found the separated valves covering the surfaces 

 of shaly limestone, also in the body of the thin limestone layers, about 

 300 feet higher in the section than the zone of Paradoxides hicksi, 

 Manuels River, Conception Bay. 



The following varieties of OrtJiis lenticidariH have been named by 

 Doctor Matthew. I find essentially the same forms present in the col- 

 lections from Sweden and Newfoundland. The variet}' strophomenoides 

 does not appear to be of varietal vahie. Many such occur in the Swe- 

 dish material. 



ORTHIS (ORUSIA) LENTICULARIS ATRYPOIDES Matthew. 



Orthis lenticularis var. atri/poides Matthew, Trans. Roy. Soc. Canada, IX, 1891, 



p. 48, pi. XII, figs. 11a, 111). 



Original description. —This form is comparatively smooth, though the ventral valve 



is sometimes concentrically wrinkled. This valve is distinguished by a median ridge 



and somewhat flattened sides, and the dorsal valve has an unusually deep sinus. 



Size of the known examples, 6 by 6 mm. and 5 by 6 mm. for the two valves. 



Formation and locality . — Same as O. lenticularis in New Brunswick. 

 «Brit. Foss. Brach., Ill, p. 232. 



