220 PALEONTOLOGY. 



ities; anterior and posterior margins subequal; the anterior margin iaving 

 the flattest curve. Axis narrow, two-thirds as long as the shield, and marked 

 by three annulations exclusive of the terminal ones; lateral lobes large, 

 concavo-convex, the margin being slightly recurved; border thin and entire; 

 four faintly-marked ribs may be counted on each side. 



This species closely resembles C. (L.) simulator in the form of the 

 middle portions of the head, but is proportionally longer in front of the 

 eye, and this latter organ smaller than would be indicated by the sinus in 

 the cheek referred to that species, while the cheeks are more oblique and 

 longer in a postero-lateral direction. The parts here associated are the only 

 ones occurring in the specimens from the locality, and there can therefore 

 be no doubt of their correct reference to the one species. 



Formation and locality. — In limestone of the Potsdam group, at Schell 

 Creek, Nevada. Collected by J. E. Clayton, esq. 



CREPICEPHALUS (BATHYUKUS ?) AKGULATUS D. Sp. 



PJate II, fig. 28. 



Entire form unknown, the specimen consisting only of an imperfect 

 glabella and fixed cheeks united. The form of the fragment is somewhat 

 quadrangular, strongly angular in front, and constricted at the anterior 

 angle of the eye-lobe. 



Glabella rounded-conical, narrowly rounded at the summit, strongly 

 and regularly convex on the surface, the height and width subequal, meas- 

 ured from the occipital furrow, entirely destitute of transverse furrows; 

 occipital ring narrow, moderately prominent, and having the appearance 

 of an obscure tubercle in the center. This feature may be deceptive. 



Fixed cheeks narrow at the eyes; palpebral lobes small, obliquely 

 situated; postero-lateral limbs short, equilaterally triangular; continuation 

 of the occipital furrow faintly marked; frontal limb short in front of the 

 glabella, wide and extended at the sides and antero-lateral angles ; the width 

 between the facial sutures equaling the entire length of the head; anterior 

 margin thickened, distinctly angular in the middle, the sides sloping rapidly 

 to the suture-lines. Facial suture cutting the anterior margin a little outside 

 of a line with the outer angle of the eye, and directed with a gently convex 



