201 



form a nintli, diifering as much from any of them as they do from each 

 other. Several of those which 1 have placed in Bikelocephalus -vvill pro- 

 bably fall into this genus, if it shall be sustained, but at present I do not 

 wish to change their generic references until more is known about them. 

 The typical species of Dikelocephalus have the last glabellar furrow, and 

 sometimes the second one, extending all across. This genus was proposed 

 by Mr. Devine, in April, 1863, but the species was placed provisionally 

 in the genus Olenus. I think it best to leave it there until we shall have 

 obtained more information concerning the affinities of the numerous species 

 of this group, now only known to us by fragments. It seems probable 

 that some of the species from the Potsdam sandstone, referred by Dr. 

 Shumard and Prof. Hall, to Qonocephalites, may belong to Loganellus. 

 The following is Mr. Devine's description :* 



Olenus ? Logani. (Devine.) 



Fig. 185. Fig. 186. 



Fig. 183. — 0. Logani. Tlie anterior part of tlie glabella, in this figure, is slightly too 



narrow. 

 Fig. 186. — An imperfect specimen, shewing the hypostoma in place. 



" Description. — The general form is oval. Head, exclusive of spines 

 semicircular, more than twice as wide as long ; truncate in front, and 

 prominently convex in the middle, with a narrow equal border, one half a 

 line in width, extended at the posterior angles with the free cheeks into 

 moderate diverging spines ; posterior margin marked by a shallow furrow, 

 reaching from the glabella outward to the free cheeks ; eyes not large, 

 smooth, and equi-distant from the front and posterior margins, and about 

 one line from the glabella ; the ocular ridge prominent, extending from 

 the eye obliquely forward to the glabella, meeting the latter at about one 

 line from the front thereof ; facial suture running obliquely from the eye 



* Description of a new Trilobite, from the Quebec group; by T. Devine, F.R.G.S., 

 O.L. Dept. Quebec : Can. Nat. and Geol., toI. 8, p. 95, April, 1863. 



o 



