22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



W'alcott, in 1907, of this species and the accompanying- subfauna 

 on Mount Bosvvorth, in the Canadian Rockies. Its position was 

 determined to be at the summit of the Lower Cambrian portion of 

 the section. 2.450 feet below the Ogygopsis klotci fauna of Mount 

 Stephen. 



The subfauna at the Blount Bosworth locaHt}' includes 



Micromitra {IphidcUa) zcapta, new f^pecies, 



Oboliis parz'its, new species, 



Acrothcle collcni, new species, 



JViinanclla simplex, new genus and new species, 



Albcrtclla boszy.'orthi, new species. 



Alhcrtella lielcna, new species, and 



B'athyuriscHS. sp. a. 



Formation and Locality. — Lower Cambrian: (i) Drift block 

 of siliceous shale on the south slope of Mount Bosworth. on the 

 "Continental Divide," one mile east of Hector, on the Canadian 

 Pacific Railway, British Columbia, Canada; and (2) Wolsey argil- 

 laceous shale, on Gordon Creek, 4 miles (2.5 km.) above its union 

 with Danaher Creek, at the southeast foot of Gordon Mountain, 

 Lewis and Clark Forest Reserve. Montana. U. S. A. 



ALBERTELLA BOSWORTHI, new species 



Plate t, Fig t -res 4-7 



This species diiiers from the associated Alhcrtella helciia in its 

 cephalon, thorax, and pygidium. In the cephalon the eye and pal- 

 pebral lobe are more elongate and nearer proportionally to the outer 

 margin. In the thorax the pleurae of the fourth segment are 

 extended into long spines instead of those of the third, as in A. 

 hclena; the pleural lobes and the entire thorax are narrower in pro- 

 portion to the length. In the pygidium there are six rings in the 

 axis instead of three or four, and two anchylosed pleural segments 

 pass into the large lateral spines instead of one. Both species have 

 seven thoracic segments and a finely granulated surface and are 

 associated in the sahie layers of shale at the ^^lount Bosworth 

 locality. 



Formation' axd Locality. — Lower Can:brian : Drift block of 

 siliceous shale on south slope of Mount llosworth. on the "Conti- 

 nental Divide ;"' one mile east of Hector, on the Canadian Pacific 

 Railwav, British Columbia. Canada. 



