PIIIMOHDIAL PERIOD. 41 



head ; width at the base, compared with its full length, about as seven io 

 eight ; sides straight or nearly so ; anterior end abiiiptly and posterior end 

 very broadly rounded ; occipital furrow well defined, and continuous with a 

 similar but rather broader furrow at each side, that extends across the cheek 

 parallel with and near the posterior margin of the head, giving that margin 

 a raised border ; la,teral furrows absent or very indistinct in adult specimens, 

 but in well-preserved young ones there are indications of foin- pairs of lobes. 

 Facial sutures curving outward and forward from the anterior ends of the 

 eyes, or from a point a little forward of their anterior ends, reaching the 

 marginal groove within the raised border of the head at points a little wider 

 apart than the eyes are at their anterior ends, then, bending somcAvhat 

 abmptly inward, they cut the anterior margin ; posteriorly, the sutures 

 extend almost directly outward from the posterior ends of the eyes, then, by 

 broad backward curves, which become more abrupt as they proceed, they 

 cut the posterior margin of the head not far from its postero-lateral angles 

 and just inside the bases of the cheek-spines. 



Eyes rather small, slightly arching outward, placed well back toward 

 the posterior margin of the head ; visual siu-faces naiTow, oui" specimens show- 

 ing no reticulations; other portions of the head apparently without sui-face- 

 markings or ornamentation, except that some specimens show a very faint 

 ridge extending transversely from the anterior end of each eye toward the 

 anterior poi-tion of the glabella, but ending at the dorsal fuiTows befoi-e 

 reaching it. 



Thorax longer than the head, measming seventeen millimeters in a 

 specimen having a head thirteen millimeters long, the same thorax measm*- 

 ing twenty-five millimeters wide at its widest part ; axial lobe depressed, 

 narrow; sides straight, about two-thirds as wide as one of the lateral lobes 

 at the anterior end of the thorax, about one-third wider at its anterior than 

 it is at its posterior end ; segments thu-teen in niimber, passing nearly or 

 quite straight across the lobe ; a shght transverse prominence usually seen 

 at each end of every axial segment near the bottom of the dorsal fun-ows, 

 producing the appearance there of a coiTugated, raised line along the whole 

 length of each furrow ; lateral lobes slightly convex, a little widest about 

 midlength ; plem-se nearly transverse with the axis of the body, nearly 



