OLENELLUS AND OTHER GENERA OF MESONACID^ 345 



fragments of the cephalon in association with OlencUus fremonti. 

 It is readily recognized by the thick, obtuse genal spines of the 

 adult, slender glabella, and small eyes. 



The known stratigraphic range of Peachella iddingsi is in the 

 arenaceous shales and interbedded siliceous limestone of the Pioche 

 formation near the top of the Lower Cambrian. At the south end 

 of the Timpahute range the following species are associated with it: 



Nisusia (Jamesella) ere eta Walcott. 

 BiUingsella highland ensis Walcott. 

 CaUazfia nevadensis Walcott. 

 Olenellus fremonti Walcott. 



On Prospect Peak, in the Eureka District, 145 miles north, 

 OlencUus fremonti and Protypiis sp. occur with it, and in the High- 

 land Range 60 miles northeast of the Timpahute Range locality 

 0. fremonti and Callaz'ia nez'adensis are found in the same hand 

 specimens. 



Formation and Locality. — Lower Cambrian Pioche formation: 

 (52) arenaceous shales aboi'e the massive-bedded sandstones of the 

 Prospect Mountain formation on the summit of Prospect Mountain, 

 Eureka District, Eureka County; (30) arenaceous shales on west 

 slope of the Highland Range at the edge of the desert, 8 miles 

 (12.8 km.) north of Bennetts Spring and about 8 miles (12.8 km.) 

 west of Pioche, Lincoln County; (6oh and 3i3g) arenaceous shales 

 and thin, interbedded limestone in the Groom Mining District at 

 the south end of the Timpahute Range, near the line between Nye 

 and Lincoln counties ; all in Nevada. 



Genus OLENELLOIDES Peach 



Olenellus (Olenelloidcs) Peach, 1894, Quart. Journ. Geol. Soc. London, 



Vol. 50, pp. 668-669, 'ind 671-674. (Described and discussed as a new 



subgenus.) 

 Olenelloides (Peach), Beecher, 1897, American Journ. Sci., 4th ser., Vol. 



3, p. 191. (Suggests that the genus represents the young of Olenellus 



or a related form.) 

 Olenelloides (Poach), Moberg, 1899, Geol. Foren. i Stockholm Forhandl., 



Bd. 21, Hiifte 4, p. 320. (Brief description of genus.) 



Dorsal shield small, elongate, narrowing from the broad, large 

 cephalon to the small, narrow pygidium. 



Cephalon large and provided with strong intergenal, genal, and 

 antero-lateral spines ; the intergenal spines appear to represent tlie 

 postero-lateral termination of the facial sutures, and the antero- 



