OLENELLUS AND OTHER GENERA OF MESONACIDJE 325 



from White, 1877, pi. 2, figs. 3b, 3a, 3c, and 3d respectively ; fig. 4, pi. 



20, is copied from Walcott, 1884, pi. 21, fig. 14; and pi. 21 is copied in 

 this paper, pi. t,6, fig. 9.) 



Olenellus gilbcrti (Aleck), Holm. 1887, Geo!. Foren. i Stockholm For- 

 handl., Bd. g. Hafte 7, pp. 514-515. (Described in Swedish. The 

 species is frequently mentioned also in the discussion of " Olenellus 

 kjerulii.") 



Olenellus iiilberii Lesley (in part), 1889, Geol. Survey Pennsylvania, 

 Report P4, Vol. 2, p. 490, figs, i and la (not fig. 2a nor the cephalons 

 represented by figs, i, la, ib, and if, these are all referred in this paper 

 to Olenellus fremonti). (Figures i and la are copied from Walcott, 

 1886, pi. 21, figs. I and la.) 



Olenellus gilbcrti (Meek), Walcott (in part), 1891, Tenth Ann. Rept. 

 U. S. Geol. Survey, pi. 84, figs, t, la-c; pi. 85, figs, ib-d ; and pi. 86, fig. 

 4 (not pi. 84, figs, id and if; pi. 85, figs. I, la, and if; and pi. 86, figs. 

 I, la-i ; ik-m = Olenellus fremonti; and not pi. 84, figs. le and Ig; 

 and pi. 85, figs. le and ig = CaUavia nevadensis) . (No text reference. 

 Figs. I and la, pi. 84, are copied from Walcott, 1886, pi. 21, figs, i and 

 la; figs. lb and ic, pi. 84, are copied from Walcott, 1886, pi. 18, figs, i 

 and la; figs, ib-d, pi. 85, are copied from Walcott, 1886. pi. 19, figs. 2, 

 2a-b, respectively; and fig. 4, pi. 86, is copied from Walcott, 1884, pi. 



21. fig. 14.) 



Olenellus canadensis Walcott (in part), 1908, Canadian Alpine Journal, 

 Vol. I, No. 2, p. 242. (Name used in list of fossils occurring in a 

 geologic section. The specimens listed include forms now referred to 

 Olenellus gilberti.) 



Olenellus gilberti Meek, Walcott, 1908, Smithsonian Misc. Coll., Vol. 53, 

 No. 5, p. 189. (Species listed in No. 2 of the Barrel Spring section.) 



Holmia rowei Walcott (in part), 1908, Idem, p. 189 (3 of section only). 

 (The specimens listed under this name from 3 of the Barrel Spring sec- 

 tion are referred in this paper to Olenellus argentus and Olenellus 

 gilberti. ) 



Olenellus claytoni Walcott (in part), 1908, Idem, p. 189. (The specimens 

 listed under this name from 6 of the Barrel Spring section are referred 

 in this paper to Olenellus claytoni and Olenellus gilberti.) 



Olenellus canadensis Walcott (in part), 1908, Idem, p. 215. (Name used 

 in section. In both cases, however, the specimens listed include forms 

 now referred to Olenellus gilberti.) 



Dorsal shield elongate ovate in outline ; strongly convex anteriorlv 

 when not compressed in the rock. Cephalon of adult semicircular in 

 outline, strongly convex in a granular limestone matrix (figs. 4 

 and 4a], moderately convex in shaly limestone [figs. i6 and 17], 

 nearly flattened and with little convexity in siliceous shales [figs. 

 I, 2, and 3] ; bordered by a rounded marginal rim that is extended 

 into somewhat slender genal spines ; the posterior marginal border 

 is rounded and narrow, and, in most specimens, it has a thickened 

 7 — w 



