l8 SMITHSOXIAX MISCiy,LAXKOUS COLLECTIONS \0L. 53 



Cambrian and 2,600 feet (792.5 m.) below tbe Upper Cambrian; 

 northwest slope of Alount Stephen, 3,000 feet (914.4 m.) above the 

 Kicking Horse River, above Field, on the Canadian Pacific Railway. 

 British Columbia, Canada. 



Order OPISTHOPARIA Beecher 



Family Paradoxid.e 



ALBERTELLA, new genus 



Dorsal shield elongate-ovate. Cephalon large, semicircular in out- 

 line, about one-fourth the length of the dorsal shield ; genal angles 

 extended into spines : cranidium subcjuadrangular in outline, with 

 long palpebral lobes and narrow fixed cheeks ; palpebral lobes elon- 

 gate, with outer rims continued across the fixed cheeks as narrow 

 ocular ridges ; glabella subquadrilateral in outline, with short lateral 

 furrows ; strong occipital ring. The facial sutures cut the posterior 

 border within the genal angles and pass inward and slightly forward 

 to the base of the eyes, thence about the palpebral lobe, and forward 

 with slight curvature to the front margin. 



Thorax with seven segments ; pleurae terminating in short spines, 

 those of the third or fourth segment in longer spines ; pleural furrow 

 with broad inner end largely filled in by an elongated tubercle. 



P3'^gidium large, with central axis divided into several rings, and 

 with the first, or first and second combined, anterior, anchylosed seg- 

 ments extended across the border into a long spine on each side. 



Genotype. — AlhcvtcUa hclciia, new species. 



Stratigraphic Range. — Upper beds of Lower Cambrian. 



Geographic Distribution. — Western Alberta, near the line of the 

 Canadian Pacific Railway, Canada, and northern ]\Iontana, in the 

 Lewis and Clark Forest Reserve. 



Observations. — AlbcrtcUa is a most interesting type of the order 

 Opisthoparia and family ParadoxidcC. It should first be com. pared with 

 the genus Zacanthoidcs Walcott,^ which, in the British Columbia 

 section, is first met with in strata 2,000 feet above the beds in which 

 AlhertcUa occurs. The cephalons of the tw^o genera are generically 

 the same. The thoracic segments are of the same type, but the third 

 or fourth segment of the thorax of AlbcrtcUa is extended into long 

 pleural spines, and the thorax has seven instead of nine segments, as 

 in Zacanthoidcs. The pygidium of AlhertcUa has a long, strong 

 spine extending from the pleural lobes of the first, or first and second 

 combined, anterior segments, and a smooth border otherwise ; the 



* Walcott, 1888, American Jour. Sci., 3d ser.. vol. xx.wi, p. 1(15. 



