OLENELLUS AND OTHER GENERA OF MES0NAC1D.E 7,21 



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

 Survey, No. 30, pp. 170-180, pi. 18, fig. ic; pi. 19, figs. 2e, 2h, and 2\\ 

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

 Olenellus gilberfi; and not pi. 19, figs. 2c, 2d, 2f, 2g = Callavia ncva- 

 densis). (Described and discussed. Figures 2e and 2i, pi. 19, are 

 copied in this paper pi. ^7. figs. 20 and 6 respectively ; fig. 2h, p. 19, is 

 copied from Walcott, 1884, pi. 9, fig. 15c; figs, i, la, and ib, pi. 20, are 

 copied from Walcott, 1884, pi. 9, figs. 15b, 15a, and 15 respectively; 

 figs. IC, id, le, ig, ih, li, ik, il, and im, pi. 20, are copied from 

 Walcott, 1884, pi. 21, figs. I, 2, 3, 4, 5, 6, 8, 9, and 7 respectively; fig. if, 

 pi. 20, is copied in this paper, pi. S7, fig- 9 ; and the specimen represented 

 by figures 2 and 2a, pi. 21, is copied with slight changes in this paper, pi. 

 37, fig. 7-) 



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

 Report P4, Vol. 2, p. 490, figs. 2a, and cephalons represented by figs. 

 I, la, lb, and if (not the whole specimen represented by figs, i and 

 la which is a true Olenellus gilhcrti). (Figure 2a is copied from 

 Walcott, 1886, pi. 21, fig. 2a; figs, i, la, ib, and if are copied from 

 figures of the same number on plate 20 of Walcott's paper [1886].) 



Olenellus gilberti Walcott (in part) [not Meeis.], 1891, Tenth Ann. Rept. 

 U. S. Geol. Survey, pi. 84, figs, id and if; pi. 85, figs, i, la, and if; and 

 pi. 86, figs. I, la-i, ik-m (not pi. 84, figs, i, la-c ; pi. 85, figs, ib-d ; and pi 

 86, fig. 4 = Olenellus gilberti; and not pi. 84, figs. le and ig ; and pi. 

 85, figs. le and ig = Callavia nevadensis) . (No text reference. Fig 

 id, pi. 84, is copied from Walcott, 1886, pi. 18, fig. ic; figs, if, pi. 84, 

 and if, pi. 85, are copied from Walcott 1886, pi. 19, figs. 2i and 2e 

 respectively; pi. 86 is a copy of pi. 20 of Walcott's paper [1886] ; and 

 figs. I and la, pi. 85, are copied from Walcott, 1886, pi. 21, figs. 2 and 

 2a.) 



Olenellus gilberti Peach, 1894, Quart. Journ. Geol. Soc. London. Vol. 50, 

 p. 671, pi. 32, figs. 9 and 10. (Mentioned. Figures 9 and 10 are copied 

 from Walcott, 1886, pi. 20, figs, if and la.) 



Holmia weeksi Walcott, 1908, Smithsonian Misc. Coll., Vol. 53, No. 5, 

 p. 187, and p. 189 (6 of section only). (The specimens listed under this 

 name on the pages mentioned are referred in this paper to Olenellus 

 fremonti.) 



Olenellus fremonti Walcott, 1908, Idem, p. 187. (Name given in a list of 

 the species occurring near Resting Springs.) 



I formerly referred specimens now included in this species to 

 Olenellus gilberti [Walcott, 1884, 1886, and 1891], but with the 

 discovery of additional material, specimens showing variations of 

 such constant character were found that it became necessary to 

 propose a new species to include them. 



The cephalon of O. fremonti differs from that of O. gilberti [pi. 

 36] : (a) in having a more expanded anterior glabella close to the 

 rounded frontal border ; (b) in having a shorter palpebral lobe, both 



