366 PALiEONTOLOGY OF NEW-YORK. 



Fig. 6. Profile viev of the same. 



Fig. 7. The iypostoma. 



Fig. 8. A part of the pygidium of this species. ' 



Geological position and locality. In the shaly limestone of the Lower Helderberg 

 group : Coeymans, Schoharie and Carlisle. 



f Jehas ])HstiiU>^us ( n. s.). 



Plate LXXVII. Fig. 9-12; and Plate LXXVIIT. Fig. 1-7. 



Head extremely ventricose : the limb is of moderate thickness, slightly 

 recurved, leaving a comparatively broad shallow groove ; margin of 

 limb pustulose. The posterior margin of the head is moderately conr 

 vex ; the occipital furrow well defined, but not deep. 



The median lobe of the glabella is extravagantly elevated, standing out 

 like a distinct protuberance in advance and above the interior lateral 

 lobes : the form at the base is broadly ovate, gently narrowing behind 

 for a little more than half its entire length to its greatest elevation, 

 and, then abruptly declining and contracting, becoming almost flat 

 between the anterior lateral lobes ; showing a crest at the margin of 

 the occipital furrow. The length and greatest breadth of this lobe are 

 about equal, and the elevation from the frontal limb to the summit of 

 the lobe is nearly equal to the width at the base in front. Anterior 

 furrow shallow in front, becoming more defined in its posterior direc- 

 tion, and, at the inward curving of the protuberant part of the median 

 lobe, is very strongly defined, while in the posterior part it is scarcely 

 below the plane of the central part of the median lobe. Anterior lobe 

 oblong, -narrow and depressed in front, gradually rising, spreading 

 out and becoming protuberant behind. Entire surface pustulose ; the 

 pustules prominent, of various sizes, sometimes rising to the form of 

 short spines. 



Two fragments, found in the same association, appear to be the movable 

 cheeks of the species : the lower side only is visible, and the marking is 

 similar to that on the lower side of the pygidium. 



