APPENDIX. 
ARTICLE I. 
DESCRIPTION OF NEW AND IMPERFECTLY KNOWN GENERA AND SPECIES OF ORGANIC REMAINS, 
COLLECTED DURING THE GEOLOGICAL SURVEYS OF WISCONSIN, IOWA, AND MINNESOTA, BY 
CRUSTACEA (TRILOBITES). 
DIKELOCEPHALUS. (N. G.) 
Generic character.—Cephalic shield semicircular, and rather flat, glabella moderately convex, equally 
wide throughout, rounded in front, divided by two furrows into three distinct lobes; these well-marked 
furrows extend quite across the glabella, and form a curve or slightly obtuse angle in the median line 
directed backwards ; the anterior lobe is partially divided by a third obscure furrow, which becomes obso- 
lete in the median line. 
Facial sutures distinct, originating at the anterior border of the cephalic shield ; they run at first 
parallel with the same, then converging in a sigmoid flexure around the eye-plate, diverge again in curved 
lines, until reaching the anterior border, they circumscribe an area of greater or less extent in front of 
the glabella. 
The cheek-plates produced at their anterior corners into spines of moderate length, as indicated by 
various detached cheek-plates, one of which, found in the buff-bed near the base of La Grange Mountain, 
is shown by Fig. 3, Tab. L., a. 
Pygidium rather deeper and about the same width as the cephalic shield; axal lobe smaller than the 
lateral, with from four to six segments; the last and largest segment sometimes obscurely subdivided by 
a faint furrow. Lateral and interlateral segments blended into a marginal flap or border of greater or 
less extent; usually, if not always, provided with caudal spines. 
Relations and differences.—The genus Dikelocephalus approaches on the whole nearest to Ogygia, but 
the middle lobe of the pygidium has fewer segments, and is much shorter and blunter; the glabella is 
not contracted posteriorly, and two transverse furrows extend quite across the glabella, in this respect 
having a greater similarity to Trilobites Sternbergii,* but from which it also differs in the anterior 
furrow, and in the basal lobe not assuming a tuberculated character. 
* See Table IIL, figs. 7 and 8, organization der Trilobiten, von Hermann Burmeister, for which Dr. Beyrich pro- 
posed the generic name of Chirurus. This genus, as given by Hawle and Corda, differs, however, in the form and 
lobes of the glabella from Burmeister’s figure of this Trilobite, and in the caudal shield there is a wide difference. 
See Tab. VI., fig. 70, of their work. 
