244 THE CHICAGO ACADEMY OF SCIENCES. 



wardly directed rounded free points, the posterior margin of the 

 pygidium back of the second pleural segments is entire and 

 describes nearly an arc of a circle. The surface of both head and 

 pygidium are covered with scattered, rounded tubercles, some- 

 what variable in size. 



The approximate dimensions of an incomplete cephalon 

 are: length 44 mm., estimated width 118 mm., convexity 18 

 mm. The approximate dimensions of an incomplete pygidium 

 are: length 80 mm., width 123 mm., width of axis at anterior 

 margin 44 mm. 



Remarks. This is perhaps the largest trilobite in the en- 

 tire Niagaran fauna of the Chicago area. It is known only 

 from incomplete heads and pygidia, although the more recent 

 collections have afforded far better material for study than the 

 original type specimens of Winchell and Marcy. In no case 

 have specimens of the head and pygidium been observed in 

 such position as to show that they belonged to the same indi- 

 vidual, but the two portions of the body have frequently been 

 found associated, and no other large heads or pygidia occur 

 in the same beds. That the two portions of the body here de- 

 scribed are really parts of one species can be assumed to be 

 established beyond reasonable doubt. The large free cheek 

 also which has been identified as a part of this species is 

 an isolated specimen, but it occurs in the same beds with the 

 heads and pygidia and can belong to no other known species. 

 In the illustration of the cephalon of the species the free cheeks 

 have been restored from the single specimen of that part of the 

 head which has been observed. 



Locality. Bridgeport. 



Metopolichas ferrisi, n. sp., pi. xxii, figs. 12-13. 



Description. Entire body sub-elliptical in outline. Crani- 

 dium sub-triangular in outline, broadly rounded or sub-trun- 

 cate in front. Glabella depressed-convex, about as wide as 

 long, bordered laterally by shallow but well-defined dorsal 

 furrows, narrowest a little back of a line joining the eyes, a little 

 broader at the occipital segment than in front; median lobe 

 occupying the entire width of the glabella in front, rapidly be- 

 coming narrower posteriorly until in line with the eyes it oc- 

 cupies only one-third the width of the glabella, posteriorly 

 it is nearly confluent with the third lateral lobes externally;, 

 first lateral furrows strong and well-defined, curving from 

 just back of the antero-lateral extremities of the median lobe, 



