320 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



worthi [pi. 39, fig. 4] and Pcedeumias transitans [pi. 32, fig-. 8], 

 except that the glabella is more expanded at the first lobe in O. 

 claytoni. 



Dimensions. — The largest cephalon in the collection has a length 

 of 13 mm., width 28 mm. The relative proportions of the different 

 parts are shown by figs. 9 and 10, pi. 40. Fig. 10 is compressed 

 laterally with the result that the glabella is narrowed and ridged at 

 the center. 



The specimens of the hypostoma show that it had a large, oval 

 body connected with a narrow neck to a strong, rounded posterior 

 border ; the sulcus within the border on each side is sufficiently strong 

 to clearly define the neck connecting the body and posterior border 



[fig--9]-" 



A few fragments of thoracic segments occur in association with 

 the cephalons, but nothing to prove more than that the pleurae had 

 a wide furrow. The test of all the specimens has been destroyed, 

 but the surface of the cephalon, as shown in the fine sandstone matrix, 

 is known to have been marked by a fine, irregular network of very 

 fine, irregular ridges. 



Olcnellus f claytoni occurs in an arenaceous shale just above a 

 mass of andesite in the Barrel Spring section [Walcott, 1908c, p. 189, 

 6 of section]. Olenellus fremonti and Scdterella sp. occur in an argil- 

 laceous shale at nearly the same horizon, but are not associated with 

 O. f claytoni. 



Formation and Locality. — Lower Cambrian: (ik and li) " Sil- 

 ver Peak Group," in arenaceous shales interbedded in the lower part 

 of No. 6 of the Barrel Spring section [Walcott, 1908c, p. 189], 1.5 

 and 1.75 miles (2.4 and 2.8 km.) south of Barrel Spring, Silver 

 Peak Quadrangle, Esmeralda County, Nevada. 



OLENELLUS FREMONTI, new species 



Plate s7, Figs. 1-22 ; Plate 41, Fig. 8 



Olenellus gilberti Walcott (in part) [not Meek], 1884, Monogr. U. S. 

 Geol. Survey, Vol. 8, p. 29, pi. 9, fig. i6a (not fig. 16 and pi. 21, fig 

 13, referred in this paper to Callavia nevadensis; nor pi. 21, fig. 14, 

 referred in this paper to Olenellus gilberti). (Described.) 



Olenelhis Iwzvelli Walcott [not MeekI, 1884, Monogr. U. S. Geol. Survey, 

 Vol. 8, pp. 30-31, pi. 9, figs. 15, I5a-c; pi. 21, figs. 1-9, and 16-17. (De- 

 scribed and discussed. Figures 15, 15a, 15b, and 15c of plate 9 are 

 copied in this paper, pi. 37, figs. 14, 16, 8, and 6a respectively. Figures 

 2-9 of pi. 21 are copied in this paper, pi. 37, figs. 10, 12, 11, 15, 13, 17, 

 ig, and 18 respectively.) 



