NO. 7 CAMBRO-ORDOVICIAN FOSSILS 233 



Dimensions. — The average length is about 6 mm. An uncom- 

 pressed specimen of the ventral valve 6 mm. in length has a width 

 of 5 mm., with a depth of about i mm. The dorsal valve is slightly 

 shorter in proportion to the width. 



Surface. — The surface is marked by fine concentric lines of growtli 

 and a few stronger concentric ridges of growth. 



Observations. — There are two or three very imperfect interiors of 

 the ventral valve that appear to have the characters of the interior 

 of Lingulella, but it may be that mure perfect specimens will prove 

 that the species is more nearly related to Obolus {^FordiniaY than to 

 Lingulella. 



Formation and locality.— Lower Ordovician : Goodsir formation 

 (lower part), west slope of Moose Creek valley, on the east slope 

 of the north ridge of Mount Mollison, elevation 6550 feet, about 10 

 miles in an air line southeast of Leanchoil on the Canadian Pacific 

 Railway ; this species is also found at about the same horizon in Ice 

 River Valley at head of East Fork, elevation 8000 feet, about 4 

 miles northwest of the Moose Creek locality, British Columbia, 

 Canada. 



Collection, J. A. Allan. 



Mr. L. D. Burling found this species, which is somewhat doubt- 

 fully identified, at about the same horizon above a cliff of the Otter- 

 tail limestone four miles southwest of the mouth of Otto Creek which 

 riows into the Amiskwi River west-northwest of Field, British Colum- 

 bia, Canada. 



Genus CERATOPYGE Corda 

 CERATOPYGE CANADENSIS, new species 



Plate 35, figs. 13-22 



This species differs from Ceratopyge forticula Sars"' in the greater 

 length of the frontal limb of the cranidium, longer palebral lobes, 

 and narrower fixed cheeks. The pygidium differs most in having a 

 shorter median lobe, broader border, and the side spine springing 

 from the first instead of the second segment. 



The thorax of C. canadensis has ten transverse segments with a 

 strong transverse furrow on each segment that terminates on each 

 pleural lobe in a blunt point about two-thirds the distance from the 

 median lobe to the slightly falcate ends of each segment. 



^ Smithsonian Misc. Coll., Vol. 53, No. 3, 1908, p. 64. 



''' Moberg and Segerberg, 1906, Medd. fran Lunds Geol. Faltklubb, Ser. B, 

 No. 2 (Aftryck ur K. Fysiografiska Sallskapets Handl., N. F., Bd. 17), pi. 

 5, figs. 2-5. 



