CONTRIBUTIONS TO PALAEONTOLOGY. 97 



GENUS PROETUS (Steininger). 



The Genus Proetus acquires its greatest development, in this country, 

 in the Upper HelJerberg and Hamilton groups. Regarding these as the 

 equivalents of the Devonian in Europe, this result is not in accordance with 

 that obtained by M. Barrande, who shows by far the greatest development 

 of species of this genus in Upper Silurian strata, and a great diminution of 

 species in the Devonian rocks. 



In the United States, as far as I know, species of this genus are rare in 

 the strata below the Schoharie grit. The species before me at this time, with 

 a single exception, have ten articulations in the thorax. Although several 

 species have granulose or papillose surfaces, I have not discovered spines or 

 lateral appendages upon any of them. Of the species described, seven are 

 entire specimens ; the others consist of heads or of pygidia, and of the 

 the thorax and pygidium. 



PROETUS CONRADI (n.s.). 



RoDY oval; length less than twice the width. Head nearly semi- 

 circular : the border is wide, a little convex, gently sloping 

 towards the margin, and prolonged behind as far as the middle 

 of the thorax. The furrow in the crust is a simple rectangular 

 depression of the surface, but, in the cast, becomes an abrupt 

 groove, with the inner side straight and the outer side strongly 

 curving. Glabella convex, somewhat ovoid, narrower in front, a 

 little longer than wide : lateral furrows obscure, the posterior 

 one curving from nearly opposite the centre of the eye backwards 

 to near the base. The facial suture bends a little outward from 

 the eye, and curves inwards towards the margin. The eye is large 

 and well developed, and somewhat elongate. 



Thorax consisting of ten segments; the axis prominent and semi- 

 circular, the annulations direct; the lateral lobes flat or slightly 

 convex for a third of their width; the ribs marked by a sharply 

 defined furrow ; the anterior limit narrower and very angular 

 on the anterior margin, filling a slight depression in the posterior 

 margin of the posterior limb : extremities obtuse. 



Pygidium semicircular; the axis very prominent, and forming about 

 one-third the width at the anterior margin and three-fourths the 

 entire length; marked by ten or eleven rings, the two anterior 

 ones being direct, and those of the middle portion bent backwards 

 and a little flattened on the summit : the lateral lobes marked 

 by four or five ribs, which are distinctly grooved in the middle 

 1861.] 13 [Senate No. 116.] 



