OLENELLUS AND OTHER GENERA OF MES0NACID.1-: 285. 



CALLAVIA ? NEVADENSIS, new species 



Plate ^S. Figs. 12-14. 



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

 Geol. Survey, Vol. 8, p. 29, pi. 9, fig. 16, and pi. 21, fig. 13 (not fig. i6a, pi. 

 g, which is referred in this paper to Olcnellus frcmonti; nor figure 14, 

 pi. 21, which is referred in this paper to Olcnellus gilbcrfi). (De- 

 scribed. Figures 16 and 13 are copied in this paper, pi. 38, figs. 12 and 

 14 respectively.) 



Olenellns gilberti Walcott (in part) [not Meek], 1886, Bull. U. S. Geol. 

 Survey No. 30, pp. 170-180, pi. 19. figs. 2c, d, f, and g (not pi. 18, figs. 

 I, la-b; pi. 19, figs. 2, 2a, 2b, 2k; pi. 20, fig. 4; and pi. 21, figs, i and la 

 = Olcnellus gilberti; and not pi. 18, fig. ic; pi. 19, figs. 2e, 2h, 2i ; pi. 

 20, figs. I, la-i, ik-m ; and pi. 21, figs. 2 and 2a = Olcnellus frcmonti). 

 (The description and discussion given includes reference to specimens 

 now referred to Callavia ncvadcnsis. Figure 2d, pi. 19, is copied in this, 

 paper, pi. 38, fig. 13; figure 2c is copied from Walcott, 1884, pi. 21, fig. 

 13 ; and figure 2g is copied from Walcott, 1884, pi. 9, fig. 16.) 



Olcnellus gilberti Walcott (in part) [not Meek], i8gi. Tenth Ann. Rept. 

 U. S. Geol. Survey, pi. 84, figs. le and ig ; pi. 85, figs. le and g (not 

 pi. 84, figs. I, la-c; pi. 85 figs, ib-d ; and pi. 86, fig. 4 = Olcnellus gil- 

 berti; and not pi. 84, figs, id and if; pi. 85, figs, i, la, and if; and pi. 

 86, figs. I, la-i, ik-m = Olenellns frcmonti). (No text reference. 

 Figures le and ig. pi. 84, are copied from Walcott. 1886, pi. 19, figs. 

 2d and 2f; fig. le, pi. 85. is copied from Walcott, 1886, pi. 19, fig. 2g; 

 and fig. Ig, pi. 85, is copied from Walcott, 1884, pi. 21, fig. 13.) 



Of this species only fragments of the cephalon and thorax are 

 known. These I referred to Oknellus gilberti [1884, 1886, and 

 1891], but in restricting- the latter species to the characters shown 

 by the type specimens [pi. 36, figs. 1-3] the specimens from Pros- 

 pect Mountain are separated and now referred to C. nevadcnsis. 

 They are distinguished from O. gilberti by the broader space between 

 the glabella and frontal rim, short eve lobes, and converging sides 

 of the glabella, particularly those of the large frontal lobe. The 

 glabella is similar to that of C. hnrri [pi. 28, fig. 9], but the marginal 

 borders differ materially in the two species. 



Callavia nevadensis is associated with numerous fragmentary 

 specimens of OleneUus frcmonti [pi. 37] and Peachella iddingsi 

 [pi. 36, fig. 17]. 



The reference to the genus Callavia is on account of the tapering 

 glabella and slender anterior glabellar lobe. 



Formation and Locality. — Lcnver Cambrian : Pioche formation 

 at the following localities: (51 and 52) at the smnmit of Prospect 

 Mountain, Eureka District, Eureka County; (30) on the west slope 

 of the Highland Range, 8 miles (12.8 km.) north of Bennetts Springs 

 and about 8 miles (12.8 km.) west of Pioche, Lincoln County; and 



