FOSSILS OF THE POTSDAM GROUP. 221 



curvature to the anterior angle of the ocular sinus; behind the eye, it is 

 directed obliquely outward to the posterior margin of the head at an angle 

 of about forty -five degrees. No indication of ocular ridges can be detected. 



There is considerable doubt as to what genus this species should be 

 referred. It lacks many of the characters of CrepicepJialus and ConocepJialites, 

 and possesses neither glabellar fui-rows nor ocular ridges. The form of the 

 glabella corresponds with many of those referred to the genus Batliyurus 

 by its author, but it differs in the direction of the facial sutures; in this 

 latter feature, it corresponds with Loganellus Devine, but differs in the 

 absence of glabellar furrows. The projecting angular frontal margin is a 

 marked and distinguishing feature. 



Formation and locality. — In the lowest beds of limestone, Potsdam 

 group, on the west side of Pogonip Mountain, White Pine, Nevada; asso- 

 ciated with Pterocephdlus laticeps. Collected by Arnold Hague, esq. 



Genus PTEROCEPHALUS Roemer. 



CONOCEPHALITES (PTEROCEPHALUS) LATICEPS H. Sp. <v/o 



Plate II, figs. 4-7. 



Entire form unknown; the remains consisting of dismembered and frag- 

 mentary parts imbedded in the rock together. 



Glabella and fixed cheeks, when united, having a somewhat elongate- 

 quadrangular form, exclusive of the postero-lateral limbs; widest at the 

 front margin, and contracted in the region of the eyes; the greatest width 

 being one-fifth less than the entire length of the head. Glabella compara- 

 tively small, highly convex and subangular along the median line, regu- 

 larly tapering from the base, including the occipital ring, to the summit, 

 which is rather abruptly truncate; width at the occipital lobe more than 

 equaling three -fourths of the entire hsight, and the width across the anterior 

 lobe of the glabella equal to a little more than one-third of the height. The 

 glabella is divided by three pairs of strongly-marked transverse furrows, 

 which extend about one-third of the width of the glabella at their respective 

 points, and are slightly inclined backward at their inner ends, separating 

 the glabella into four pairs of distinct lobes, which decrease regularly in 



