Contributions to Palceontology. 



153 



species is much narrower, and the fixed cheeks are wider and more 

 elevated. 



A movable cheek (Plate ii, f. 41), occuring in the same associa- 

 tion (and with scarcely any fragments of other fossils), I have 

 referred to this species with doubt. 



There is also a pygidium in the same specimens, which I have 

 referred to this species. It is more than twice as wide as long j the 

 axis is conical, abruptly elevated, and marked by six annulations 

 besides the anterior articulating joint. The sides are nearly flat, 

 and marked by four ribs which are flattened and faintly grooved. 



Dr. Shumard has very kindly sent me a specimen of the species 

 described by him as Dikelocephalus latifrons, consisting of the large 

 frontal limb and the principal part of the glabella (Plate ii, fig. 40). 

 On comparison with seven or eight individuals of the species which 

 I have identified with- Crepicephalus? wisconsensis of Owen, I can 

 find no characters which separate the two. From its conical glabella 

 and oblique furrows, I place it with Conocephalites. It is clearly 

 related generically to Lonchocephalus (Conocephalites) hamulus of 

 Owen. 



The great width of frontal limb shown in Dr. Owen's figure of 

 Crepicephalus wisconsensis is a character not possessed in an equal 

 degree by any other species except Conocephalites hamulus, and, 

 approximately, by Conocephalites diadematus. The contour of the 

 limb in the two last is different from that of the figure of Dr. Owen, 

 which corresponds with the specimens I have referred to that species. 

 In the figure cited (Tab .1, f. 13), the frontal limb is equal in length 

 to the width of the glabella near the front; a feature which corre- 

 sponds with the specimens I have figured, and with others of the 

 same species. In the specimen of Dr. Shumard, the length of the 

 frontal limb is proportionally a little greater; but I do not regard this 

 difference as of specific importance. 



PLATE II. 



Fig. 39. The glabella and fixed cheeks of a small individual. 



Fig. 40. The frontal limb and part of the glabella of a large individual, 

 showing radiating striae on the frontal limb. This figure is from 

 Dr. Shumard's specimen. 



Fig. 41. A cheek (associated with the glabella at Trempaleau), showing 

 the direction of the facial suture in its posterior extension. 



[Trans, v.] 20 



