144 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



is broad and prominent, marked by about five rings besides the 

 articulating one : the lateral lobes slope abruptly downwards, then 

 curving they spread in a broad flattened border (which is every- 

 where incomplete in the specimen) ; each side is marked by four 

 ribs, exclusive of the anterior one; the two forward ribs are divided 

 through a part of their length, and the four appear as gentle undu- 

 lations in the border. 



This species possesses the essential characteristics of glabella given by 

 Dr. Owen for Dikelocephalus, except the slight convergence of the 

 sides ; and I have therefore referred it to that genus. 



The glabella, frontal limb and fixed cheeks resemble D. pepinensis; but 

 the occipital ring in this one is more convex, and bears a spine ; the occi- 

 pital furrow is not so direct, while the posterior glabellar furrows are more 

 oblique : the second or median pair of furrows can be traced across the 

 glabella, while the anterior ones are slight indentations in the margin, like 

 the anterior and middle ones of D. pepinensis. The dorsal furrow is more 

 sharply impressed at the sides ; turning rectangularly in front of the gla- 

 bella, which is more truncate, and separated by a narrower furrow from the 

 more convex frontal limb. 



These features are important distinctions, since in this one the approach 

 to the Genus Conocephalites, in the form of glabella and glabellar fur- 

 rows, is very perceptible. The pygidium has the general expression of D. 

 minnesotensis, being somewhat more convex, but the minor characters are 

 very different. 



This species occurs at Trempaleau, in calcareo-magnesian sandstone, 



near the middle of the formation. 



I 



DIKELOCEPHALUS MISA ( n. s.). 



PLATE VIII, FIG. 15; AND PLATE X, FIGS. 4, 5, and ? 6, 7 & 8. 



Glabella prominent, somewhat conical, truncate at the apex, the 

 length about equal to its width at base, which is more than 

 one-third greater than the width in f#ont. Three pairs of furrows 

 are visible ; the posterior ones oblique and sometimes slightly 

 marked across the middle, leaving the posterior lobes deeply 

 separated and directed forward at the extremities. Median 

 lobes and furrows directed a little forward ; anterior furrows 

 faintly impressed, leaving a very narrow anterior lobe ; occipi- 

 tal furrow well defined, straight in the middle, and curving a 

 little upwards at the sides : occipital ring wider in the middle, 

 curving forward towards the extremities. 



Facial suture directed slightly inwards from the anterior margin, 

 and thence curving gently outwards, it follows the line of the 



