NO 5 CAMBRIAIsT TRILOBITES 409 



NEW FORMATION NAME 

 CHISHOLM SHALES 



Type locality. — Vicinity of Chisholm Mine and Half Moon Gulch, 

 2 to 3 miles northwest of Pioche, Lincoln County, Nevada. 



Derivation. — From Chisholm Mine. 



Character. — Pinkish-colored, compact, argillaceous shale with a 

 few intcrbedded layers of limestone 3 to 15 inches in thickness. 



Thickness. — About 100 feet in vicinity of Chisholm Mine and 125 

 feet in the Highland Range section. 



Organic remains. — Middle Cambrian. At the Chisholm Mine 

 (locality 31) : 



Eocystites ? longidactylus Walcott 



Micromitra (Iphidclla) paiimila (White) 



Obolus (Wcstonia) clla (Hall and Whitfield) 



Lingulella dubia (Walcott) 



Hyolithes billingsi Walcott 



Zacanthoides lypicalis Walcott 



Ptychoparia piochcnsis Walcott 



Anomocare ? parvum Walcott • 



Bathyiiriscus howelli Walcott 



Dolichomctopiis productus (Hall and Whitfield) 



Observations. — The stratigraphic position of the Chisholm shale, 

 as noted in the Highland Range section,' is about 1,200 feet (370 m.) 

 above the Lower Cambrian with 3,000 feet of Cambrian limestones 

 above it. In the upper portion of the latter limestone I found in 1887 

 the following (locality 88) : 



Oicoiella aiiiiqiiata (^^'hitfield ) 

 Sinuopea, 3 undt. spp. 

 Hyolithes attenuatus Walcott 

 Hyolithes ? corrugatus Walcott 

 Hyolithes curvatus Walcott 

 . Dikelocephalus cf. D. minncsotcnsis Owen 

 Saukia pepinensis (Owen) 

 Enrekia dissimilis (Walcott) 

 Conaspis^ sp. undt. 

 Arethusina ?F amcricana Walcott 



This is the fauna listed on page 35, Bull. 30, U. S. Geol. Surv., 

 1886, and page 318, Bull. 81, U. S. Geol. Surv., 1891. The species 



'Bull. U. S. Geol. Surv., No. 81, 1891, p. 318, Bed No. 21. 

 ^ New genus. 



