FOSSILS OF THE CLINTON GROUP. 523 



A pygidium found at the same quarry was 3.6 mm. broad and, minus 

 the spines, had a length of 1.7 mm. Its entire anterior margin was bor- 

 dered by a distinct segmental ridge, and from a similar ridge along the poste- 

 rior border projected the posterior spines. In the center of the pygid- 

 ium lay the inversely triangular median segment on either side of which, 

 further enclosed by the ridge-like border just mentioned, lay a depressed, 

 area. Of spines, there were at least six, the two exterior being larger, 

 but their total length being unknown. The pygidium may not be entire. 



Small gabellae occur at Huffman's quarry, south of Dayton, and also 

 at the Centerville quarry, northeast of the village. At the latter locality 

 a fragment of the free cheek was also found. These small glabellas are 

 constant in character and are probably the glabellas corresponding to the 

 free cheek and p3*gidium already described. The glabella has two 

 strongly defined, strongly convex lobes on either side, there being no ad- 

 ditional segmentation of the glabella anterior to these lobes as in A. 

 Ortoni. The fixed cheeks are also strongly defined and bold, curving in 

 a semi-lunar way from the occipital groove to about the middle of the 

 anterior lobe of the glabella. The ocular ridge is low and narrow at the 

 eye, becoming broader and stronger anterior to the fixed cheeks and still 

 more so in passing before the anterior of the two lateral lobes of the 

 glabella. The groove anterior to the ocular ridge and the glabella, 

 behind the anterior border of the head, is broad and distinct, especially 

 laterally. The anterior border of the head is markedly convex in front 

 of the glabella, thus projecting beyond the general margin of the head. 

 The occipital furrow is broad, and the occipital segment is broad but does 

 not give evidence of posterior prolongation. The most marked feature 

 is the coarse, close, granular ornamentation on the glabella, its lobes, the 

 fixed cheek, the anterior portion of the ocular ridge, and the middle por- 

 tion of the occipital ridge. Length of the Huffman's quarry head, 4.5 

 mm.; of the Centerville head, 6 mm. 



All specimens referred to this species cxur in the upper shaly 

 courses of the Clinton. 



Proetus determinatus. Foerste, 



(Plate 2(3, Fig 5; Plate 27, Figs. 2, 3, 3a). 



This species was described in the Bulletin of Denison University, 

 Vol. II. from the Soldiers' Home quarries. Since then a well marked 

 glabella has been found at Brown's Quarry. A free cheek with rather 

 broad border, and prolonged postero-laterally into a spine, was found at 

 the last named quarry and may belong to the same species. The occi- 

 pital segment is separated from the glabella by a strong occipital groove; 

 towards either side of the segment a less deep groove crosses the segment 

 obliquely, giving rise to two lateral lobes within the area of this segment. 

 A specimen recently found at the Soldiers' Home shows that the glabella 

 is low and but moderately convex, and not strongly elevated at the 

 margins above the general curvature of the head. The glabella is defined 



