THE NATURAL HISTORY SURVEY. 237 



form, the two median spines are also lacking which are present 

 in C. palmata. The specimens referred to a variety of this 

 species by van Ingen, from the St. Clair limestone of Arkansas, 

 differ from the typical form in the shape of the median lobe of 

 the glabella and should doubtless be considered as a distinct 

 species for which his varietal name depauperata may be used. 

 Localities. Joliet and Chicago Drainage Canal near Lemont. 



Genus 8. DICRANOPELTIS Corda, 1847. 



Cephalon tuberculate, sub-triangular in outline. Glabella 

 well-defined by the dorsal or axial furrows, the median lobe 

 more or less protuberant in front, extending backward to the 

 occipital furrow. First lateral furrows extending backward to 

 the occipital furrow, deep and strong anteriorly, sometimes 

 becoming shallower and less well defined posteriorly. Second 

 pair of lateral furrows obsolete so that the first and second 

 lateral glabellar lobes are combined into a single pair of large 

 compound lobes. Third pair of lateral lobes well defined, lying 

 between the compound anterior lobes and the occipital furrow; 

 behind these are a pair of basal or occipital lobes. Pygidium 

 rather large, axis elevated with two annulations anteriorly and 

 continued posteriorly in a flattened post-axial area; lateral 

 lobes flattened, with three pairs of grooved pleura each with a 

 free point, the posterior pair sometimes not completely marked 

 off posteriorly from the post-axial area. 

 Dicranopeltis decipiens (W. & M.), pi. xxn, figs. 10-11. 



Description. Cephalon very convex, sub-triangular in 

 outline, produced laterally in rather strong, flattened spines 

 which extend obliquely outward and backward, breadth between 

 the extremities of the lateral spines more than twice the length. 

 Glabella sub-pentagonal in outline, flattened on top posteriorly, 

 the anterior slope strongly convex and slightly protuberant, 

 lateral slopes gently convex. Dorsal furrows deep and strong 

 anteriorly, becoming shallower posteriorly; describing a convex 

 curve from the anterior margin to the junction with the third 

 lateral glabellar furrows, beyond which they describe a slightly 

 concave curve past the outer extremities of the third lateral 

 and the occipital lobes to the occipital furrow. Median lobe of 

 the glabella widest at the anterior margin where its breadth is 

 nearly 'equal to that of the glabella at its mid-length, broadly 

 convex in front, becoming narrower posteriorly where it forms 

 a little less than the median third of the glabella at the junction 



