422 REPORT ON THE STATE CABINET. 



curve ; the distance between the sutures on the anterior margin but 

 little less than in front of the eyes. 



This species, in comparison with /. artnatus, I. bmriensis and J. imperator, 

 has the glabella more elongated, while it is less convex than I. insignis, 

 with shorter, and laterally more produced, palpebral lobes. The posterior 

 position of the eye lobe is likewise a distinguishing feature. 



Formation and Locality. — In limestone of the Niagara group, at Wau- 

 watosa; and a single specimen of doubtful locality, received from Mr. I. 

 A. Lapham, has the aspect of the Bridgeport rock. 



GENUS BRONTEUS, Goldfuss. 

 Bronteus acamas, n. s. 



PLATE XXI, FIGS. 19, 20; PLATE XXV, FIG. 21. 

 JSronteus occasus, Winch. & Marct. Mem. Bost. Soc. of Nat. Hist., I, p. 104, Plate iii, fig. 12. 



A cast of the head is broad ; depressed convex ; the anterior jaortion 

 plain ; dorsal furrow extending a little more than one-third the entire 

 length. A single glabellar furrow, with a distinct anterior lobe, are visi- 

 ble. The palpebral lobe is comparatively broad and moderately elevated. 



The pygidium is somewhat semi-elliptical or parabolic, wider than 

 long; the axis is short, somewhat semi-oval, with one or more ti'ansverse 

 furrows near the anterior margin, while the terminal portion is marked 

 by two faint longitudinal depressions, which are scarcely defined grooves. 

 The median rib, at its origin, is about twice as wide as the lateral ones, 

 increasing gradually, and below the middle of its length more rapidly, 

 to the margin ; where it is four or five times as wide as at its origin, and 

 entirely simple. There are seven lateral ribs on each side, which are 

 very slightly elevated, and the four anterior ones curve gently forward. 



The specimens are for the most part casts of impressions, so that the 

 entire surface characters cannot be ascertained. The head is imperfect, 

 the occipital ring and cheeks being broken off; but there are several 

 nearly entire pygidia in the collection. 



The pygidium of this species resembles the Bronteus planus of Corda, 

 as illustrated by Barrande (^Systeme Silurien du centre de la Boheme, PL 

 xlii, fig. 34, and PI. xxxviii, fig. 3), and it is difficult to point out dis- 

 tinguishing characters. The head associated with these pygidia is more 

 nearly like that oi Bronteus tenellus (Barrande, ut sup., PI. xlvii, figs. 36, 

 37); but it differs from that in some important particulars. 



