136 



Contributions to Palczontology. 



Dorsal furrow deep and strongly denned, particularly 

 in the middle of its length : fixed cheeks very narrow 

 at the sides, and arching longitudinally ; the palpebral 

 lobe separated from the cheek by a long sigmoid groove 

 which reaches nearly to the groove in the posterior 

 limb : the latter is broad, and the border narrow. The 

 frontal limb has a wide and deep groove in front of the 

 glabella, with an abruptly raised narrow anterior border, 

 the whole being curved suddenly downwards at the an- 

 terior lateral angles. 



This species is conspicuously distinct from any of the others by 

 its very gibbous glabella, which is nearly equal in length and width. 

 The posterior and medial glabella-furrows are well marked, but 

 there is no distinct indication of the anterior one. 



Specimens containing this fossil were derived from a loose mass 

 of sandstone at Trempaleau, apparently from the beds near the lo- 

 cality, since it was little worn. From the character of the rock, its 

 position is probably between the extreme lower and middle fossili- 

 ferous beds. 



The three preceding species have the form of glabella 

 which is characteristic of Conocephalites, and the facial 

 suture cuts the frontal contour at a point distant from the 

 apex. In the last one, however, the direction of the 

 suture-line in its posterior course is different from the 

 others, and there is a distinct groove defining the palpe- 

 bral lobe ; a feature not observed in the other two. 



In the following species, the glabella is conical, and 

 more or less distinctly marked by oblique furrows. The 

 suture-line partially cuts the anterior border at a point 

 distant from the apex, but a narrow portion of the cheek- 

 border extends along the frontal limb nearly or quite to 

 the apex. This course of the suture-line produces a slop- 

 ing or curved outline from the apex to the lateral margin 

 of the frontal limb. The fixed cheeks are very narrow, 

 and prominent towards the eye ; but in none of them are 



