NO. 3 CAMBRIAN AND OZARKIAN TRILOBITES 73 



slightly different front. B. nonius has a flatter rim, but the glabella 

 is marked off in much the same way except that it is more expanded 

 anteriorly. The head is less convex in longitudinal cross-section and 

 the palpebral lobes are also slightly smaller. 



The free cheek (fig. 9) assigned to B. nonius has preserved the 

 extension of the doublure for a considerable distance beyond the 

 cheek. The suture is intramarginal. 



The pygidia associated with B. nonius are not unlike those of 

 B. collieana, except that the axial and pleural ribs are less well 

 developed. 



Formation and /oca/zYy.— Ozarkian : Mons fonnation. (65y) north 

 side of Clearwater Canyon, 2 miles (3.2 km.) from divide at head. of 

 canyon and about 21 miles (33.8 km.) in an air line north, 2° west, 

 of Lake Louise Station on the Canadian Pacific Railway, Alberta, 

 Canada. 



This species occurs in ic of the Clearwater section, 426 feet (129.8 

 m.) above the base of the Mons formation and 970 feet (295.7 ^'^•) 

 below the summit. 



BOWMANIA, new genus 



Description, — Only the glabella of the type species is known. Due 

 to the meager material the following generic description must be 

 regarded as tentative. 



The glabella is cylindrical, rounded in front and a little less than 

 half the length of the head. Two pairs of very short glabellar furrows 

 are present. Eyes small, situated back of the middle of the glabella. 

 Ocular ridges strong. Frontal border wide, convex, with a narrow 

 rim, and covered with fine, irregular lines. 



Facial suture unknown. The frontal rim is of an even width 

 throughout, which proves that the suture was not intramarginal. 



Genotype. — Arethusina americana Walcott. 



Range. — Upper Cambrian. 



BOWMANIA AMERICANA (Walcott) 



Plate 15, figs. IS, 16 



Arethusina americana Walcott, 1884, Monogr. U. S. Geol. Surv., Vol. 8, p. 62, 



pi. 9, fig. 27. (Described and illustrated.) Brogger, 1886, Geol Foren. 



Stockholm Fornhandl., bd. 8, p. 206. (Mentioned.) 

 Harpides ? americanus Freeh, 1897, Leth. geog., th. i, Leth. Pal., 2, p. 44, 



•footnote. (Generic reference changed.) 

 Atilacopleiira americana Raymond, 1913, Ottawa Nat., Vol. 26, p. 6. (Generic 



reference changed.) 



See original description for details. 



