376 TWENTIETH REPORT ON THE STATE CABINET. 



groove, extended posteriorly into spines which are equal in length to 

 the glabella. 

 Glabella large, depressed convex, widening in front to twice its width 

 at the posterior margin, divided into lobes by three pairs of transverse 

 furrows exclusive of the occipital furrow, which is distinct and cuntinu- 

 ous. The two posterior furrows are distinct at the sides, but do not 

 extend entirely across the glabella except in very faint depressions. The 

 anterior furrows are deep, very distinct, situated a little anterior to the 

 eyes, extending each about one- third across the glabella, and giving to 

 the frontal lobe a transversely elliptical outline. The occipital ring is 

 narrow, ornamented on the middle by a single short sharp spine. Eyes 

 very prominent, short reniform, containing about thirty -five vertical 

 ranges of lenses, the middle one of which have nine each. Cheeks small, 

 prominent on the anterior portion, marked near the posterior margin by 

 a deep groove, the continuation of the occipital furrows. Thoracic seg- 

 ments unknown. 

 Pygidium somewhat elongate triangular, extended posteriorly into an 

 acute spine : central lobe or axis marked by ten or twelve narrow 

 rings ; the lateral lobes less prominent, marked by ten flattened ribs, 

 which terminate in a narrow flattened margin. Eight of these ribs are 

 double throughout their entire length ; the posterior ones are directed 

 obliquely backwards. 



This species somewhat resembles D. limulurus {Phacops limulurus, Pal. 

 N. Y., PI. 67, f. 1); but differs in the proportionally larger glabella, the 

 larger and more prominent eyes, and the extension of the anterior border. 

 The pygidium is less rounded on the anterior margin, the spine is more 

 obtuse, the flattened margin outside of the ribs is narrower, and the num- 

 ber of ribs on the lateral lobes is greater. 



Geological formation and locality. In Niagara limestone, at Waukesha, 

 Wisconsin. 



CERAURUS NIAGARENSIS. 



PLATE 21 (12), FIG. 10. 

 Ceraurus insignis : page 334 = p. 30 original paper. 



A careful camparison of our specimens with the figures of C. insignis, 

 given by Barrande, shows certain differences in the general form of the 

 glabella, the direction of the furrows and form of posterior lobes, which I 

 am inclined to regard as of specific importance, and therefore propose 

 another specific name. The New-York and Wisconsin specimens of this 

 species preserve the same characteristics. 



In the collection loaned to me for examination by Prof. Winchell, I 

 have discovered the hypostoma of a Ceraurus attached to the front of an 

 imperfect glabella, which I infer belongs to this species. This appendage 

 diff'ers from the hypostoma of C. insignis in being more rounded anteriorly, 

 and is not so deeply notched at the sides, while the border just anterior to 

 the notch is not expanded as in the European species. 



