FOSSILS OF THE HUDSON EIVEE GEOUP. 109 



length, separated from the anterior lobe by deep, narrow furrows. An- 

 terior lobe transversely sub-ovate, prominent ; middle and posterior lobes 

 obsolete ; occipital ring narrow, distinctly defined. 



" Eyes very prominent, with five lenses in the vertical range, but the 

 number of vertical ranges can not be determined; palpebral lobe de- 

 pressed. The outer border of the movable cheeks is thickened and 

 rounded, and the space between the border and the eye depressed. The 

 posterior spines long and broad, reaching to the sixth thoracic segment. 



"Thorax with the axial lobe highly convex and the lateral lobes 

 strongly geniculate, sub-equal in width, rapidly tapering posteriorly 

 from the fourth or fifth segment. Segments curved forward on the top 

 of the axial lobe, and the furrows on the pleura strongly marked. 



" Pygidium obtusely pointed behind, the lateral borders inclosing an 

 angle of about one hundred and twenty degrees, the anterior border 

 rounded; the number of articulations not clearly defined, but apparently 

 numbering about ten or twelve, besides the terminal one ; those of the 

 lateral lobes have been more numerous. 



" The entire surface, so far as can be seen on the specimen, has been 

 finely pustulose." 



The species is peculiar in the shortness of the cephalic shield, and in 

 the apparent absence of the middle and posterior, lobes of the glabella. 

 It dififers conspicuously from D. callicephala, of the Trenton limestones of 

 New York, in the possession of spines on the posterior angles of the 

 cephalic shield. From D. Carleyi, Meek (Palaeontology of Ohio, Vol. I., 

 p. 170, pi. 14, fig. 2), it differs in the greater breadth of the head and gla- 

 bella, and in the short, broad pygidium. 



As the original specimen from which the description quoted above was 

 taken is the only one seen by us, we can not add any other features to 

 those already given. 



Formation and locality: In the* shales of the Hudson Eiver group, upper portion, 

 near Lebanon, Ohio. 



G-ENUS PROETUS, Steininger. 

 Proetus paeviusculus. 



Plate 4, fig. 18. 



Proetus parviusculus, Hall ; Extr. 20th Eept. State Cab., p. 17, 1866 ; 24th Eept. State 

 Cab., p. 223, pi. 8, flg. 14. 



" Body, in general form, broadly ovate, widest across the base of the 

 cephalic shield. Head sub-lunate, produced into long, sharp spines at 



