112 PALEONTOLOGY OF NEW YORK. 



border. The specimen is somewhat crushed across the base of the glabella, 

 but sufficient is retained to show evidence of strong basal lobes similar to 

 those in P. ovifrons, and above these, indications of two pairs of lateral 

 furrows. 



The eyes arc elongate, relatively narrow, and are closely appressed to the 

 glabella. 



Tbe single example has an axial length of 5 mm., a length to the apex of 

 the cheek-spines of 9 mm., and a width of 7.5 mm. 



Distribution. Upper Helderberg group. In the decomposed Corniferous chert, 

 a1 North Caj uga, Province of Ontario. 



PROiiTUS [?] PLANIMARGINATUS. 



PLATE XXIII. FIG. 12 



Proetus planimarginatus, Meek. Proc. Acad. Nat. Sci. Phila., p. 89. 1871. 



atus, Meek. Palaeontology of Ohio, vol. i, p. 233 ; pi. xxiii, figs 3 a, b. is"::. 



Ptgidium semi-elliptical in outline: length to width as 3 to 5. Surface de- 

 pressed-convex on the sides, elevated along the axis. Border moderately 

 broad, Sal and sulcate near the edge. 



The axis, on the anterior margin, has about one-fourth the width of the 

 shield, and tapers evenly to a blunt extremity considerably within the poste- 

 rior margin. It bears ten distinct, and traces of two or three indistinct 

 annulations; these are transverse over the median area, slightly angulated 

 and inclined posteriorly toward the margins. 



The pleura each bear nine low, narrow annulations, separated by broad, 

 shallow sulci, and each annulation is sulcate upon its summit for its entire 

 length. The annulations become obsolete toward the posterior extremity, 

 leaving the post-axial area smooth. 



The type specimen of the species is a smooth cast of the lower surface, 

 and from Mr. Meek's observations upon other specimens, the dorsal surface 

 appears to have been devoid of ornamentation. 



Dimensions of the original: length 10 mm., width 25 mm. 



