50 



entire width of the head, measured on the curve, the anterior 

 margin slightly sinuous near the suture. Eyes close to the 

 posterior margin, large, conical, the palpebral lobe projecting 

 laterally at right angles to the axis ; genal angles rounded. 



The thorax has ten segments, the axis regularly and moder- 

 ately convex, its sides gradually converging to the pygidium; 

 the lateral lobes have a flat space outside of the dorsal furrow, 

 reaching to the fulcra of the pleura, which is equal to one-third 

 the width of the axis ; at this point the pleura bend abruptly 

 downwards. The pygidium has less than half the area of the 

 head, broadly rounded on the posterior side and broadly trun- 

 cated laterally, almost at right angles to its anterior margin. 



A single entire specimen only has been seen ; and this gives 

 the following measurements: 



Entire length of a rolled specimen, measured on the curve, 

 four and a quarter inches: of this the head measures more 

 than two inches; its direct length being one inch and three- 

 eighths. The thoraxiiand pygidium measure two and a half 

 inches; the width of the head to the extremities of the eyes, 

 measures two and a quarter inches. 



Geological Formation and Locality. In the "Buff limestone" 

 of Beloit, and at Mineral Point, Wisconsin. I have also seen 

 the same species from Rockford, Illinois. 



I am indebted to Rev. John Murrish, of Linden, for a very 

 fine specimen. 



GENUS CALYMENE, Dauian. 



(JALYMENE mammilata, (n. s.) • 



JJescripiion. Form of the entire body unknown. Cephalic 

 shield broadly semi-elliptical, the posterior margin nearly 

 straight, the anterior border extended in front of the glabella 

 in a broadly rounded, thickened projection, which is abruptly 

 recurved at the margin, and marked on each side by a mam- 

 miliform tubercle about half way between the antero-lateral 

 angle of the glabella and the edge of the border. The glabella 

 is proportionally small, broad at base, rounded in front, lobed 

 at the sides by three pairs of transverse furrows; the posterior 

 lobes extend about one -third across the glabella, and are di- 

 rected backwards, forming two rather large tubercles ; the two 

 anterior pairs are small, and extend but a short distance from 

 the margin of the glabella. The centre of the glabella is 

 prominent, the sides nearly parallel to the anterior angles, 

 which are slightly extended laterally; occipital furrow distinct, 

 bent forward in the middle. Cheeks very prominent, giving 



