306 PALAEONTOLOGY OF NEW-YORK. 



Fig. 6. The caudal extremity and a few articulations of the abdomen from which the crust ia 



separated, showing the difference of form thus produced in this part of the fossil. 



The faint line beyond this shows the limit of the impression of the margin and spine 



in the shale. 

 Fig. 7. The inner surface of the crust (separated from the specimen fig. 6), showing its extension 



laterally in a thick border beyond the marks of articulation, and posteriorly into the 



spine. 

 Fig. S. The eye of this species enlarged, showing the elevation, form and structure of the surface. 



Position and locality. Shale of the Niagara group, Lockport. 



667. 5. CERAURUS INSIGNIS. 



Pl. LXVII. Figs. 9 & 10. 

 See page 300 of this volume. 



Buckler nearly semicircular, with the posterior angles extended into sharp spines ; glabella 

 clavate, lobed ; anterior portion very convex, a little extended laterally beyond the posterior 

 portion, and causing the longitudinal furrow to form a curve at this point ; the posterior lateral 

 furrow oblique, reaching to the centre, and joining the transverse furrow at the base of the 

 glabella ; the posterior lobes are thus circumscribed, and triangular in form ; the anterior and 

 second furrow are sharp, and almost directly transverse or slightly arched ; surface granulate, 

 granulations xmequal in size ; surface of cast punctate. 



The fragments of this species correspond so well with the figures of Beyrich, that I can have 

 no doubt of the identity of our species with the Bohemian one. It is only recently that I have 

 discovered, among some old collections, the two fragments figured, and I had prcviouly supposed 

 that the genus was confined to the Lower Silurian period*. The fragments preserve so strongly 

 the characteristics of Ceraurus, that I can not hesitate for a moment to refer it to that genus, 

 which has precedence in point of time over Cheirurus ; and the figures of this and other 

 species given by Beykich show conclusively that the two are identical. 



Fig. 9. The central portion of a cephalic shield, preserving the form and proportions of the 

 glabella and the outer crust in part, with the spine at one of the posterior angles. 



Fig. 10. Another similar fragment, where the base of the eye is preserved on one side, with the 

 posterior spine of the buckler. The anterior portion is broken, and the extension in 

 front may be due to pressure. 



Position and locality. In the shale of this group at Rochester. 



• It U only since the publication of the first volume of the Palaeontology of New- York, that I have seen the papers 

 of Beyrich cited above. 



