FOSSILS OF THE CAMBRIAN. - 55 
Formation and locality—Cambrian. Prospect Mountain Group, upper 
beds of the Secret Cation shale on the east side of Secret Canon, Eureka 
District, Nevada. 
Ptychoparia Oweni M. & H. 
Plate x, figs. 3, 3a. 
Arionellus (Crepicephalus) Oweni Meek & Hayden, 1861. Proc. Acad. Nat. Sci. Philad., 
vol. xiii, p. 436. 
Arionellus ? Oweni Meek & Hayden, 1862. Amer. Jour. Sci., 2d Series, vol. xxxiii, 
p. 74. 
Agraulos Oweni Meek & Hayden, 1864. Pal. Upper Missouri, p. 9, figs. A, B, C. 
Agraulos ? Meek & Hayden, 1864. Pal. Upper Missouri, p. 10, pl. i, fig. 4. 
OD 
Conocoryphe (Ptychoparia) Gallatinensis Meek, 1873. Sixth Ann. Rep. U.S. Geol. Sury. 
Territories, for the year 1872, p. 485. 
Crepicephalus (Loganellus) centralis Whitfield, 1877. Prelim. Rep. Pal. Black Hills, 
a Whitfield, 1881. Rep. Geol. and Resources Black Hills of Da- 
kota, p. 341, pl. ii, figs. 21, 24. 
I was somewhat surprised on bringing together the types of Arionellus 
= Ptychoparia Owent, 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 ? —————, 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 = 
Ptychoparia 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, 
