28O THE CHICAGO ACADEMY OF SCIENCES. 



the anterior position of the front margin of the glabella, the 

 cheeks in this species not being connected around the front of 

 the glabella by a flattened border. It is an unusual type of 

 Dalmanites in the American Silurian faunas, the only other 

 known occurrence being in the St. Clair limestone of Inde- 

 pendence County, Arkansas, the species in the two regions 

 apparently being identical. 



Locality. Chicago Drainage Canal, near Romeo and near 

 Lemont. 



Dalmanites verrucosus Hall. pi. xxv, figs. 6-7. 



Description. Head with genal spines attached, sub- 

 crescentiform in outline, the outer margin describing a semi- 

 ellipse, the surface depressed-convex. Glabella depressed-con- 

 vex, key-stone shaped, broadest in front, limited by well-defined 

 dorsal furrows; frontal lobe transversely sub-elliptical in outline, 

 occupying about one-half the entire glabella, its length nearly 

 two-thirds its width; first lateral lobes wedge-shaped in outline, 

 nearly twice as wide at the dorsal furrows as at the inner ex- 

 tremities of the lateral furrows ;. second lateral lobes quadrangu- 

 lar, smaller than the first; third lateral lobes similar to the 

 second but a little smaller; lateral furrows deeply impressed, 

 not continuous across the median third of the glabella, the 

 anterior pair extend obliquely inward and backward from 

 their points of origin on the dorsal furrows and are a little less 

 sharply defined than the two posterior pairs which are trans- 

 verse in their direction, the posterior pair are connected across 

 the median portion of the glabella by a slight depression. Oc- 

 cipital furrow deeply impressed laterally, shallower in the middle 

 and arched a little forward. Occipital segment about equal 

 in width to the posterior glabellar lobes, its surface level with 

 the glabella. Cheeks convex, sub-triangular in outline; the 

 marginal border rather broad and flattened, continuous around 

 the anterior extremity of the glabella, abruptly separated from 

 the convex portion of the cheeks by the marginal furrows, and 

 produced posteriorly into rather broad genal spines ; the posterior 

 cheek furrows are strong and deep, originating at. the dorsal 

 furrows and continuing to the marginal furrows with which 

 they coalesce in front of the bases of the genal spines; eyes 

 prominent, their summits a little higher than the surface of the 

 glabella, their faceted surface describing a sub-semicircle. 



Pygidium sub-triangular or sub-elliptical in outline, ab- 

 ruptly produced posteriorly into a sharp spine of moderate 



