155 



eyes and form of the glabella in both at once separating 

 them. 



The presence of the eye-line or ocular ridge allies the 

 Tasmanian Trilobite to Hall's G. minutus,% from the 

 Potsdam Sandstone, but they do not otherwise agree. Again, 

 another American species, C. diadematus, Hall,|| possesses 

 an ocular ridge, and other characters noticeable in G. Ste^phensi. 

 I suspect that, whatever may be the ultimate systematic 

 position of G. Stephensi, the latter will prove to be congeneric 

 with it. 



I have appended to the description of the cephalic shield 

 named in honour of Mr. Stephens, that of a free cheek, 

 constantly associated with the former. In one case only has 

 any appearance of a free cheek in contact with other portions 

 of the head represented itself, and although in a bad state of 

 preservation, it appears to demonstrate the unity of the parts 

 in question. 



Genus DIKELOCEPHALUS. I). D. Owen. 



DIKELOQEPHALUS TASMANICUS (sp. uov.) 



(Fig. 4.) 



Sp. c^ar.— Pygidium semi-elliptical, moderately convex, and 

 strongly facetted at the anterior angles. Axis tapering 

 gradually, extending almost to the posterior margin, and of 

 six distinguishable segments and a terminal appendage, more 

 than half the width of the pleurae at its anterior or wider 

 end. Side lobes, or pleurae, of about eight coalesced and bent 

 down segments, the first broader than any of the others. 

 Limb broad, produced on each side, opposite the fifth segment, 

 into a strong tapering, diverging, and slightly curved spine, 

 extending beyond the posterior limit of the tail tor a distance 

 equal to more than half its entire length, exclusive of the 

 spines. 



Ohs. The segmentation, broad border or limb, and single 

 lateral spines, lea.ve no doubt of the relation of this tail to 

 the genus DiJcelocephalus. The spines, however, are much 

 longer than in the generality of Bihelocephali, and in this 

 particular resemble some of the North American Trilobites, 

 referred by Hall to Conocephalites. For instance, G. Jowe7isis 

 has a pair of long curved spines, but the other characters 

 do not v^^incide with the Tasmanian tail. Another species, 

 named by Hall simply DiJcelocephalus has similar spines, 

 but is otherwise distinct. 



The remains of no other Trilobite have been met with in 

 these Caroline Creek beds, at all comparable in size to the 

 present fossil, except the head previously described as 

 Conocephalites ? Stephensi. The latter has been shown not to 



§ 16th Annual Report, State Cabinet of N. York, 1863, PI. 8, F. 5. 

 II Ibid, PI. 7, Figs. 36—38. 



