210 rAL.T:OMTOLOGY. 



tlian tlie breadth across the eyes, but generally a little narrower, and the 

 autero-lateral angles are rounded by the extreme point of the movable 

 cheeks, which extend in front on the upper side of the carapace, while the 

 fixed cheeks are as a general thing reduced to their minimum breadth. 



Another iratui-e which prevails throughout the entire group is the well- 

 marked, and often strong, ocular ridges, a feature rarely noticed among the 

 specimens from Wisconsin. The absence of this feature in these latter may, 

 however, be in great part owing to the unfavorable material and condition 

 of preservation, they being all casts in a loose, frlalde, and often coarse sand, 

 not fitted for retaining the more faintly marked characters of the organisms; * 

 while the matrix from these western localities is a hard and very solid lime- 

 stone, containing a considerable amount of sand in some parts, and extremely 

 difficult to separate from the organic remains. 



The features above noticed are mostly those pertaining to Dr. D. D. 



Owen's genus Crepicephalus as shown in the figures, cited by him as generic 



(Geol. Iowa, Wis, and Minn., plate lA, figs. 10 and 18); and we see no 



sufficient reason why they shoxdd not be considered as of generic importance. 



Ihit whether the name Crephephahis shall be retained is not so readily 



determined. The gi^nus Loganellus Devine, 18G3, is a very closely allied, 



if not identical, form; but as no entire individuals have been obtained, either 



fi-oni the AYisconsin or these more western localities, except of C. (L.) Hagnei, 



herein described, it is impossible to satisfactorily determine their true generic 



relations. There would seem, howevei-, to be no doubt hi regard to the 



generic identity of the latter, or of G. (X.) qnndrans, with Loganellus Logani 



Devine, and from the great similarity of these to the dismembered parts of 



the other species, we are inclined to consider them as all pertaining to one 



genus. 



Crepicephalus (Loganellus) IIaguei n. sp. 



P!ati' II, fi-s. M-15. 



T>ody In-oadly ovate in form, widest across the base of the head, 

 broadly rounded in front and ra[)idly tapering behind to the small i)ygi- 

 dium, strongly trilobed and moderately convex. 



* Since tliis matter has been in llie piinttrs' liamls, 1 have examined many fresbly 

 collected specimens from several localities of this formation in Wiscousin, and find, on 

 mast of them, the ocular ridges strongly marked.— 11. P. W. 



