The Genus Bronteus in the Chemung Rocks of New York. 



Communicated to James Hall, State Geologist, by J. M. Clabke. 



Trilobitic remains are of so rare occurrence in the Chemung faunas, 

 that the discovery of a new form is attended with an unusual degree 

 of interest. Hitherto we have known but two, possibly three, species 

 of trilobites from these rocks; Cyphaspis losvis, Hall, of which, it is 

 understood, but a single specimen has been seen ( Vide Palaeontology 

 of N. Y., Vol. VII, p. 150, pi. xii, fig. 29), Phacops nupera, Hall, a species 

 of doubtful value, the original specimen being imperfect in those 

 particulars which, if retained, would serve to prove or disprove its 

 specific validity. All positive evidence furnished by the original, 

 points to the identity of Ph. nupera with Ph. rana, Green. The writer 

 has been informed by Mr. H. S. Williams, of the occurrence of 

 undoubted Phacops rana in certain horizons of the Chemung group, 

 a fact not generally known at the time of the preparation of Volume 

 VII of the Palaeontology of New York. 



To these meager evidences of the trilobite fauna of the upper 

 Devonian is to be added the form under consideration, an incom- 

 plete pygidium of a species of Bronteus, from the beds of the Lower 

 Chemung in the town of Prattsburgh, Steuben county. In the Ameri- 



Fig. l. Bkonteus senescens (enlarged to two diameters), 

 can Devonian this genus has proved exceedingly rare; indeed, a single 

 pygidium, and a fragment of the epistomal doublure from the Tully 

 limestone in Onondaga county, have furnished the sum of our 

 knowledge of its post-Silurian existence in this country. This Tully 



