NO. 5 CAMBRIAN TRILOBITES 35I 



This small species is somewhat similar to B. {Poliella) anteros (pi. 

 46, fig. 5) ; it differs in having seven instead of nine thoracic seg- 

 ments, more abrupt terminations of the thoracic segments, a propor- 

 tionally larger glabella and broader pygidium. 



Formation and locality. — Middle Cambrian: (55c) Spence shale 

 member of the Ute formation; about 50 feet (15.2 m.) above the 

 Brigham quartzite, and 2,755 ^^^t (839.7 m.) below the Upper Cam- 

 brian, in a ravine running up into Danish Flat from Mill Canyon, 

 about 6 miles (9.6 km.) west-southwest of Liberty and 15 miles (24.2 

 km.) west of Montpelier, Bear Lake County, Idaho. 



BATHYURISCUS (POLIELLA) OCCIDENTALIS (Matthew) 



Plate 46, fig. 3 



Dolichometopus occidentalis Matthew, 1899, Trans. Royal Soc. Canada, 2d 



ser.. Vol. 5, Sec. 4, No. 2, p. 49, pi. 2, fig. 2. (Describes species and 



illustrates with a somewhat diagrammatic figure.) 

 Bathyiiriscus pupa Matthew, 1899, Idem, p. 51, pi. 2, fig. 5. (This appears 



to be a laterally compressed specimen of B. occidentalis.) 

 Bathyiiriscus occidentalis Walcott, 1908, Smithsonian Misc. Coll., Vol. 53, 



p. 41. (Places species in genus Bathyuriscus.) 

 Bathyuriscus occidentalis Walcott, 1908, Canadian Alpine Jour., Vol. I, 



No. 2, pi. 3, fig. 2. (Illustrates type specimen.) 



This small and rare species has a relatively broader glabella, nine 

 thoracic segments, and a short pygidium with one or two rings in 

 its axial lobe ; the triangular swelling in the pleural furrow next to 

 the dorsal furrow is scarcely visible. Only one specimen, and that a 

 matrix, has been found and identified. This has a length of 12.5 mm. 



For comparison with B. (Poliella) anteros (pi. 46, fig. 5), see 

 description of the latter (p. 349). 



Formation and locality. — Middle Cambrian : (14s) Stephen forma- 

 tion ; Ogygopsis shale, northwest slope of jNIount Stephen, above 

 Field, on the Canadian Pacific Railroad, British Columbia, Canada. 



BATHYURISCUS (POLIELLA) POWERSI, new species 



Plate 46, fig.i 

 This very clearly defined species is similar to B. haydeni in cra- 

 nidium and thorax, except that it has 11 thoracic segments and a 

 more expanded frontal lobe to the glabella. Its greatest variation is 

 in the pygidium, which has but three rings and a terminal section in its 

 axial lobe and corresponding smaller pleural lobes and a rather strong 

 border. The base of a small spine is preserved at the center of the 



