(30 CANADIAN PERIOD. 



convex, indistinctly defined externally by the broad, nearly flat margina 

 border; their inner sides more clearly defined, especially their anterior 

 portions, by the dorsal furrows. Sui'face apparently smooth ; but this 

 character, as well as the remainder of the body, is unknown. 



Length of the pygidium from the front end to the base of the caudal 

 spine, fifteen millimeters; width of the same between the antero-lateral 

 angles, twenty-two millimeters. 



This species is closely related to Asaphus (3Ie(/alaspis)ffoniocerct(s'Meek; 

 but it difi'ers from that species in its less distinctly triangular outline, its 

 greater proportionate width, its proportionally narrower axis, and rather 

 more distinct dorsal foiTows. In general aspect, the pygidium of our species 

 resembles that of a Dalmanites, but the obscure trilobation and segmenta- 

 tion separate it from that genus. It has not so complete a consolidation of 

 the component elements of the pygidium as Asaphus has ; and no striation 

 of the under surface of the marginal border has been observed, such as is 

 common in the genus Asaphus. 



Position and locality. — Strata of the age of the Quebec group of Canada; 

 Queen Spring Hill, Schell Creek range, Nevada. 



Collected by Mr. J. E. Clayton. ' • 



Family (?). 



Genus DICELLOCEPHALUS Owen, 1852. 



Dicellocephalus ? flagricaudus White. 



Plate III, fig. 8 a and 6. 



Dicellocephalus flagricaudus White, 1874, Exp. & Surv. west 100th Merid., Prelim. Rep. 

 Invert. Foss., 12. 



Pygidium contracted-fan-shaped; lateral lobes each consisting of thi'ee 

 segments dii'ected backward; the inner one of each side lying close to the 

 dorsal furrow, nearly parallel with the axis of the body or converging a little 

 posteriorly, and becoming obsolete upon each side of a small, but com- 

 paratively wide, sloping border that extends around the posterior end of 

 the axial lobe. 



The middle pair of segments commence at the dorsal furrow of each 



