116 
PALEONTOLOGY OF NEW YORK. 
species and cannot be confounded with any of the allied species of Proetus in 
the adjoining formations. Pygidia considerably larger than those found in New 
York, but agreeing in essential details with that of the type of P. Haldemani, 
occur in the Hamilton limestone at Long River, Michigan. 
The specimens of this species from the Eureka District of Nevada, described 
by Mr. Walcott (op. cit.), consist of two fragmentary cephala and two pygidia, 
which agree in every essential feature with the type, except in the character of 
the frontal border of the head, which in the typical form is flat, while in these 
specimens it is strongly reflexed. This feature may eventually prove of specific 
importance. 
More recently certain pygidia from the west slope of the Ural Mountains 
have been referred to this species by Tschernyschew (Die Fauna des mittl. und 
ober. Devon am West-abhange des Urals, loc. cit.). So far as may be judged from 
the figures alone, these appear to be considerably shorter and more elliptical, 
with a relatively wider and stouter axis than in the type specimen. 
Distribution. Hamilton group. In the Goniatite limestone of the Marcellus 
epoch; Cherry Valley, Otsego county; Manlius, Onondaga county. In the 
Hamilton limestones ; Long River, Michigan. In the Devonian (Hamilton ?) 
limestone in Pennsylvania, and in the Eureka District, Nevada. 
Proetus macrocephalus. 
PLATE XXI, PIGS. 10-21; AND PLATE XXIII, FIGS. 30, 31. 
Proetus macrocephalus. Hall. Descr. New Species of Fossils, etc., p. 77. 1861. 
Proetus macrocephalus, Hall. Fifteenth Kept. N. Y. State Cab. Nat. Hist., p. 105. 1862. 
Proetus macrocephalus, van. a.. Hall. Fifteenth Kept. N. Y. State Cab. Nat. Hist., p. 107. 1862. 
ProeUis macrocephahcs. Hall. Illustrations of Devonian Fossils, pi. xxi, tig-s. 10-21. 1876. 
General Form and Proportions. Outline elliptical. 
Surface depressed-convex, distinctly and sub-equally trilobate. Length 
to width as 1.5 to 1. 
Cephalon sub-semicircular or lunate, margin slightly thickened and reflexed, 
produced at the genal angles into thin acute spines. Surface very convex in 
normally preserved specimens; depressed in the usual state of preservation. 
Length to width as 1 to 2. 
