NO. 5 CAMBRIAN TRILOBITES 357 



having a distinct furrow crossing from the inner anterior side to 

 the posterior outer side ; the anterior outer half of each segment has 

 a sloping faceted surface and the segments terminate in a more or 

 less sharp falcate end. 



Pygidium large with the anterior margin arched slightly forward ; 

 axial lobe convex with from five to seven transverse segments and a 

 terminal section ; pleural lobes with a broad margin and more or less 

 faintly marked by shallow, narrow furrows that serve to indicate the 

 outward extension of the anchylosed segments of the axial lobe. 



Surface of the type species and of all species as far as known 

 punctate (except possibly D. acadicus Matthew) and also marked 

 by very fine irregular raised lines. 



Dimensions. — Fragments of D. suecicus indicate that the entire 

 dorsal shield was about 65 mm. in length in some specimens. Ex- 

 amples of D. tontoensis in the collection are 95 mm. in length. 



Genotype. — Dolichometopus suecicus Angelin. 



Stratigraphic range. — As far as known Dolichometopus is con- 

 fined to Middle Cambrian formations. 



Geographic distribution. — The genotype D. suecicus comes from 

 Andrarum, Sweden. Dolichometopus acadicus Matthew, a some- 

 what closely related species to D. suecicus, is found iri the province 

 of New Brunswick, Canada. Dolichometopus productus ranged on 

 both the Atlantic and Pacific sides of the North American Continent. 

 It has its representative in northern Georgia and eastern Tennessee ; 

 northern Arizona and northern Utah. Dolichometopus tontoensis is 

 found in the Grand Canyon of the Colorado in northern Arizona. 

 Dolichometopus bion in southern Idaho ; D. baton and D. ? bessus in 

 central Montana, and D. boccar along the Rocky Mountain Conti- 

 nental Divide on the line of the Canadian Pacific and Grand Trunk 

 railroads. In Eastern China the genus is abundantly represented by 

 D. {?) alceste, D. {f) deois, D. {?) derceto, and D. {?) dirce. 



Observations. — The species referred to Dolichometopus and Ba- 

 thyuriscus in this paper have long been confused by me and by 

 others. Now I think we may define Dolichometopus as characterized 

 by seven thoracic segments, a glabella almost free from lateral 

 furrows, and a pygidium only faintly marked on its axis by trans- 

 verse furrows that are extended onto the pleural lobes only as a 

 trace, if at all. The genus Bathyuriscus (restricted) has from eight 

 to nine thoracic segments, a more expanded glabella marked by dis- 

 tinct lateral furrows, and a pygidium with distinct axial rings and 

 anchylosed segments on the pleural lobes. 



