CONTRIBUTIONS TO PALEONTOLOGY. 87 



twice the length. Eight distinct rings mark the axis, with two or 

 three indistinct ones below : the posterior extremity is rounded and 

 obtuse, and separated from the expanded border by a marked groove. 

 The lateral lobes are marked by ten ribs, which terminate in a 

 moderately wide border. The grooves between the ribs are rounded, 

 well defined, and wider at their abrupt termination on the border. 

 The posterior border is obtusely angular on the margin in the direc- 

 tion of the rib next to the last on each side, and a little concave on 

 the exterior between these points, and appearing as if bent upwards, 

 having a slightly arching contour when viewed in profile from 

 behind. 



This species resembles the D. selenurus and D. CBgeria; but the head is 

 less extended in front, the denticulations are shorter, and apparently but 

 nine in number ; and the caudal extremity is broadly emarginate or slightly 

 concave, but has no spiniform processes. There are other minor distinctions, 

 which will be shown in final illustrations. 



Geological formation and locality. In the Hamilton group : near Ske- 

 neateles lake, N.Y. 



BALMANIA MACROPS (n.s.). 

 Head short, lunate : frontal lobe of glabella very wide, nearly 

 twice as wide as long; anterior and middle lobes nearly equal; 

 posterior lobe small; occipital ring large. Eyes proportionally 

 very large; the elevation of the one measured being -^^^ of an 

 inch, the longitudinal diameter at base -^-^^^ and at summit ■^^-^. 

 There are sixteen or more lenses in a vertical line ; thirty -four 

 ranges can be counted, and there are apparently one or two more : 

 the lenses are prominent, and their area not limited by elevated 

 lines. 



The only specimen positively determined to belong to this species, is an 

 imperfect head : this is distinguished from D. selenurus and D. cBgeria by 

 the broader frontal lobe of the glabella, and proportionally much larger 

 eye ; it differs from D. adspectans in the broader base and less elevation of 

 the eye, and the larger and more prominent lenses. 



Geological formation arid locality. In limestone of the Upper Helder- 

 berg group : Schoharie. 



1861.] 



