FOSSILS OF THE CAMBRIAN. 



f>5 



Formation and locality. Cambrian. Prospect Mountain Group, upper 

 beds of the Secret Canon shale on the east side of Secret Canon, Eureka 

 District, Nevada. 



Ptychoparia Oweni M. & H. 

 Plate x, tigs. 3, .5 a. 



Arionelliis (Crepicephalus) Oiceni Meek & Hayden, 186L. Proc. Acad. Nat. Sci. Philad., 

 vol. xiii, p. 430. 



Ariondlua ? Oweni Meek & Ilu.ulen, 1802. Amer. Jour. Sci., 2d Series, vol. xxxiii, 

 p. 74. 



Agraulos Oweni Meek & Hayden, 1804. Pal. Upper Missouri, p. 9, figs. A, B, C. 



Agraulos t Meek & Hayden, 1804. Pal. Upper Missouri, p. 10, pi. i, fig. 4. 



Conocoryphe (Ptychoparia) Gallatinentsis Meek, 1873. Sixth Ann. Rep. U. S. Geol. Surv. 

 Territories, for the year 1872, p. 485. 



Crepicephalus (Loganellus) central-is Whitfield, 1877. Prelim. Rep. Pal. Black Hills, 

 p. 10. 



Crepicephalus contrails Whitfield, 1881. Rep. Geol. and Resources Black Hills of Da- 

 kota, p. 341, pi. ii, figs. 21, 24. 



I was somewhat surprised on bringing together the types of Arionellus 

 = Ptychoparia Oweni, Conocoryphe = Ptychoparia Gallatinensis, and Crepi- 

 cephalus = Ptychoparia centralis, to find that they were representatives of one 

 somewhat variable species. The types of P. Oweni and P. centralis are abso- 

 lutely identical, while P. Gallatinensis is only a variety of P. Oweni that 

 shows a wider range of variation, owing to the fact that we have a larger series 

 of specimens representing it. One of these variations is shown in the Black 



Hills specimen figured by. Meek and Hayden as Agraulos f , and 



labeled (probably by Mr. Meek) in the collection of the Smithsonian Insti- 

 tution as Conocephalites sp. ? 



The Nevada species is the same as that from the Gallatin River, Mon- 

 tana, and the Black Hills of Dakota. It presents much the same variations 

 in size, and the presence or absence of the glabellar furrows is a noticeable 

 feature in each. Some of the younger specimens resemble Conocephalites = 

 Ptyclioparia arenosus Bill., from the Potsdam sandstone of Vermont, but dif- 

 fer in the width of the fixed cheeks and frontal limb. 



P. Oweni ranges through nearly 4,000 feet of strata, being found in the 

 Prospect Mountain limestone of the 700-foot level of the Richmond mine 

 and well up in the Pogonip Group on the ridge east of the Hamburg mine, 



