2 1 2 p aLyEONTOLOG y. 



tlic thorax ; segments distinct, moderately elevated, s-liglitly flattened, and, 

 on the older specimens, having obscure flattened tubercles at the outer 

 extremities ; lateral lobes convex, flattened on the inner half, and gradually 

 rounding on the outer portion, becoming flattened and slightly concave 

 Loward the free ends of the pleura. Pleura straight for nearly one-half 

 ilieir length, beyond which they are directed backward with an increasing 

 curvature to the free ends ; fuiTows broad and deep, occupying nearly the 

 entire breadth of the pleura on the straight portion, beyond which they are 

 narrowed, and become obsolete on the flattened part of the extremities. 



Pygidium small, elliptical, the anterior and posterior margins nearly 

 equally rounded ; outer angles obtuse ; surface convex, strongly trilobed ; 

 axis not quite one-third of the entire width, prominently convex, and reach- 

 ing nearly to the postei'ior margin, marked by three rings exclusive of the 

 terminal ones; lateral lobes depressed-convex, marked by three pairs of 

 furrows, which are cur\ed backward, and become obsolete before reaching 

 the margin. 



This species diifers from ConocejihaUles (Conocorj/pJir) Kinffil Meek in 

 its broader fonu, proportionally wider axis, and smaller pygidium ; in hav- 

 ing one less thoracic ring, a broader and less conical glabella; and in the 

 broader furrows of the pleura, as well as in several points of minor import- 

 ance. It also bears considerable resemblance to Logancllus Lofjani Devine 

 (Pal. Foss. Canada, vol. 1, pp. 200 and 201), but differs conspicuously in the 

 ])roportionally larger cephalic shield, larger cheek-spines, and in wanting 

 the extended extremities of the pleura, as in that species. 



Formation and lovalUy. — In dark-colored limestone of tlie I'otsdam 

 group, on the west side of Pogonip IMountain, and near French Mine, 

 White Pine District, Nevada. Collected by Arnold Hague, esq. 



CREI'ICEPUAI.US (LoGANELLUS) NITIDI'S 1). sp. 

 riatell, fiKs. 8-10. 



(Ilaltclla pyramidal, scpiarely truncate in front; lateral margins nearly 

 straight; hciglit alx.ve the occipital furrow less than the width at the base, 

 and the anterior end ecpuil in width to the entire height, including the 

 occipital ring, separated from the fixed cheeks by well-defined, rather deep, 



