NO. 5 CAMBRIAN TRILOBITES 335 



Stronger ; (c) in having one or two more rings on the median lobe of 

 the pygidium, and in having the first segment of the pygidium 

 extended as a short spine beyond the border. 



There are nine thoracic segments and six segments in the axis of 

 the pygidium that continue across the pleural lobes to the margin. 



The largest specimen of the dorsal shield in the collection has a 

 length of 40 mm. 



Formation and locality. — Middle Cambrian : (58J) Stephen forma- 

 tion; about 1,900 feet (579 m.) above the Lower Cambrian and 3,100 

 feet (945 m.) below the Upper Cambrian, near the base of the hme- 

 stone forming 2 of the Stephen formation, on the east side of Movmt 

 Stephen about 3,000 feet (914 m.) above the Canadian Pacific Rail- 

 way track (north of the tunnel) , 3 miles (4.8 km.) east of Field ; and 

 (6ij) yellow-weathering band of calcareo-argillaceous shale; west 

 slope of Mount Field, near Burgess Pass ridge, about 3,000 feet 

 above Field, on Canadian Pacific Railway, British Columbia, Canada. 



BATHYURISCUS ANAX, new species 

 Plate 48, figs. I, la-d 

 Bathyunscus productus (Hall and Whitfield) Walcott (In part), 1886, Bull. 

 30, U. S. Geol. Surv., pi. 30, figs, i, la, \b, ig, ih. (The specimens 

 illustrated by the above figures are all from Big Cottonwood Canyon, 

 Wasatch Mountains, and are now considered as belonging to the species 

 B. anax.) 

 This fine species is readily separated from the species now referred 

 to as Dolichometopus productus by the form of its glabella and the 

 character of its pygidium. It also has one more thoracic segment. 

 It differs from B. atossa in having one less thoracic segment (8), a 

 longer palpebral lobe and broader axial lobe on thorax and pygidium ; 

 B. atossa also has an occipital spine that has not yet been seen on 

 B. anax. It is closely related to B. rotundatns except that it has one 

 less thoracic segment and longer palpebral lobes. 



The specimens from Big Cottonwood Canyon (30a) show only 

 the cranidium and pygidium, but these appear to be identical with 

 similar parts from further north in the Wasatch Range (55^), and 

 they are not identical with Dolichometopus productus, with which I 

 placed them in 1886. 



The largest entire dorsal shield has a length of 40 mm., and the 

 outer surface is slightly roughened by shallow pits. 



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

 horizon of the Ute formation; about 100 feet (30.5 m.) above the 

 Brigham quartzite, at the mouth of the first small canyon south of 



