FOSSILS OF THE POTSDAM GEOUP. 213 



dorsal furrows. Surface regularly convex, with a scai'cely perceptible 

 angularity along the median line, which is seen only by the reflection of 

 light from the surface; glabellar furrows nearly obsolete, or the posterior 

 pair visible only on the most critical examination. Occipital furrow nar- 

 row, and the ring distinct and rounded. 



Fixed cheeks rather narrow, prominent at the eye, and rapidly declin- 

 ing in front, and more especially to the antero-lateral angles of the frontal 

 limb; ocular ridges distinct Frontal limb, including the narrow, elevated, 

 and rounded border, as long as the width of the anterior end of the glabella, 

 and strongly convex between the rim and glabella, from which point it 

 rapidly descends to the margin; very wide in front between the suture- 

 lines, and rapidly contracting to the eyes. Posterior lateral limbs triangu- 

 lar, their lateral extension greater than the width from the eye to the basal 

 border of the head. Eye-lobes small. 



Facial sutures cutting the front margin considerably outside of the line 

 of the eye, the angles of the limb slightly rounded; from this point the line 

 is directed strongly inward to the eye, behind which it again passes outward 

 and downward to the posterior margin, making an angle of about thirty-five 

 degrees with the base of the head. Surface of the crust of the head smooth. 



The pygidium associated with the glabellas in the same frag'ments of 

 rock is suborbicular or obscurely pentangular, slightly transverse; the 

 posterior margin regularly curved; junction of the anterior and posterior 

 lines forming obtuse angles; the anterior margin is also angular on the 

 shoulders. Axis small, convex, about two-thirds the length of the shield, 

 and marked by four annulations exclusive of the terminal ones; lateral lobes 

 flattened, broad, slightly convex on the inner half; anterior margin bordered 

 by a strong flattened rib, extending to the lateral angles; three other obscure 

 ribs mark the convex portion; border broad and flattened. 



The species differs from any other herein described in the short, trun- 

 cate glabella, associated with the laterally-expanded frontal limb, and want 

 of glabellar furrows. There are none of the Wisconsin species which 

 approach it in the combination of these features. C. lowensis. is perhaps as 

 closely related as any, but the eyes are much larger, and the lateral limbs 

 very much longer and narrower. The pj^gidium has much the appearance 



