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. A\ alcott (op. tit), 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, he. tit.). 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, FIGS. 10-21; and PLATE XXIII, FIGS. 30, 31. 



Proetus macrocepJialus, Mall. Deser. New Species of Fossils, etc., p. 77. 1861. 



lug, Halt,. Fift th Rept. N. Y. State Cab. Nat. Hist., p. 105. 1S62. 



/,( '•"'■'■'•' ■■■'" ■-■■ vslt. a.. Halt,. Fifteenth Rept. N. Y. State Cab. Nat. Hist., p. 107. 1862. 



. Hall. Illustrations of Devonian Fossils, pi. xxi, figs. 10-21. 1876. 



Genebal Form and Proportions. Outline elliptical. 



Surface depressed-convex, distinctly and sub-equally trilobate. Length 

 to width as 1.5 to 1. 



Cephai.on 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. 



