CONTRIBUTIONS TO TALiEONTOLOGY. 105 



wide gently concave surface. The glabella is ovoid, very convex ; the length 

 a little greater than the width at base. The anterior and middle glabellar 

 furrows are not conspicuous, but appear as gently curving lines, and origi- 

 nating near the anterior angle of the eye. The posterior furrow causes a 

 slight indentation, and, curving backwards, reaches nearly to the posterior 

 margin (all the furrows being visible in the cast). The occipital furrow is 

 narrow ; the occipital ring of medium width, and narrowing so as to become 

 obsolete near the dorsal furrow ; the nodes of moderate size and prominence. 



In well-preserved specimens the thorax is about once and a half as wide 

 as long, the axis and lateral lobes being nearly equal in width ; while in 

 flattened specimens, the axis is wider than the lateral lobe. Axis rounded 

 and prominent ; the lateral lobes flat for nearly half their width, and not 

 depressed at the dorsal furrow. ( Other specimens, from compression, have 

 an apparently wider axis and a depression along the dorsal furrow.) The 

 pygidium is semioval, two - thirds as long as wide : axis prominent, and 

 marked by nine or ten rings ; the lateral lobes with seven ribs, which are 

 grooved along the centre, and terminate in a narrow convex border. Surface 

 granulose. 



This species, when compared with the P. roivi, shows the distinctions 

 pointed out by Mr. Conrad of the less prominent glabella and smaller 

 occipital nodes. Compared with the P. clarus of the Corniferous limestone, 

 there are few conspicuous dift'erences ; the most important, as far as observed, 

 being in the form and extension of the border of the head. This species, 

 however, is separated by one thousand feet of deposits, in which no similar 

 form of Proetus is known to occur. 



Geological formation and locality. In the TuUy limestone, near Ovid 

 in Seneca county, N.Y. Collected by John Chambers. 



PKOETUS MACROCEPHALUS ( n. s.). ■ 



Entire body elongate oval-ovate; the head, thorax and pygidium 

 nearly equal to each other in length. Head large, somewhat semi- 

 circular, with the border produced behind in short sharp spines; 

 the anterior portion of the border marked by a semicircular 

 groove in advance of the glabella; the margin thickened and 

 recurved, marked on its upper, lower and lateral faces by sharp 

 parallel elevated striae or ridges which are separated by regular 

 rounded grooves. Glabella prominent, ovate; width and length 

 about as five to six : anterior and middle furrows distinct; and 

 the posterior one, extending almost directly inwards from a point 

 a little posterior to the middle of the eye, turns abruptly and 

 extends to the posterior margin, leaving a large ovate distinctly 



1861.] U [Senate No. 116.] 



