ULEXELLUS AND OTHER GENERA OF MESON ACID.E 415 



PAGE 

 OlcnclUis .' claytoiii, new species 319 



FiG^ 9. An hypostoma associated with this species. The back margin 

 appears to be denticulated. X 4- Locality (i/O- U. S. Na- 

 tional Museum, Catalogue No. 568i3rt. 



10. A cephalon flattened by compression in arenaceous shale. X 2. 



Locality (n'). U. S. National Museum, Catalogue No. 568136. 



11. A cephalon slightly distorted by lateral compression. X 2. 



Locality (li). V. S. National Museum, Catalogue No. 568130-. 

 The specimens represented by figs. 9 to il are from locali- 

 ties (1/ and i^), both ne:;r Barrel Spring, Silver Peak Quad- 

 rangle, Nevada. 



OlcneUus argciilus. new species 314 



Fig. 12. Under side of genal spine showing rounded doublure. Natural 

 size. L^. S. National Museum, Catalogue No. 56812a. 



13. Dorsal view of a genal spine and portions of the marginal 



borders and broad cheek. Natural size. U. S. National 

 ^Museum, Catalogue No. 56812&. 



14. A small head with the genal angle on a line with the front of 



the glabella. X -■ U- S. National Museum, Catalogue No. 



568 1 2f. 

 15 and 15(7. Top view and side outline of a cephalon, showing the 



heavy marginal rim and large spherical anterior lobe of the 



glabella. X 2. LT. S. National Museum, Catalogue No. 56812c?. 

 16. Enlargement of the surface. X 6. U. S. National Museum, 



Catalogue No. ~)68i2e. 



The specimens represented by figs. 12 to 17 are from locality 



(i7'), 3 miles north of Valcalda Spring, Esmeralda County, 



Nevada. 



Peachclla iddingsi (Walcott) 343 



Fig. 17. Illustration of the type specimen of the species. X 2. U. S. 

 National Museum, Catalogue No. 15407a. 



This specimen was first figured by Walcott, 1884, pi. 9, fig. 

 12. In both instances the broken portions have been restored 

 from other specimens. 

 iS. Lender side of a genal spine and connected parts of the cheek. 

 Natural size. U. S. National Museum, Catalogue No. 15407&. 

 19. A small cephalon, X 2, with a more slender spine than that 

 of the larger cephalon represented by fig. 17. U. S. National 

 Museum, Catalogue No. 15407c. 



The specimens represented by figs. 17-19 are from locality 

 (52), Prospect Peak, PZureka District, Nevada. 



