300 



PALEONTOLOGY OF NEW-YOEK. 



666. 3. PHACOPS TRISULCATUS. 



Pl. LXVl. Fig. 3 a, b. 



Calymenel trisulcata. Hall, Geol. Rep. of 4th District N. York, 1843, pag. 72, fig. 9 ; des. p. 74. 

 Compare Phacops (^Calymenel') DowningicB, Murchison, Sil. System, pag. 655, pl. xiv, fig. 2. 



Buckler semicircular, posterior angles obtuse ; front rounded ; glabella lobed, the divisions 

 Singular, separated by narrow sharp grooves ; eyes small ; caudal shield short, with few arti- 

 culations ; surface? 



The only specimen of this species which has fallen under my observation is the small one 

 figured, and in this the surface is partially crushed and the markings obliterated. The divisions 

 of the glabella correspond with P. downingice, but the front of the buckler is more rounded 

 and the caudal shield shorter. It is possible, however, that larger and better preserved speci- 

 mens may show a more intimate relation between the two. 



Fig. 3 a. The individual of the natural size. 



Fig. 3 b. Enlargement of the buckler, several ribs of the body, and the caudal shield ; in which 

 the characters are distinctly represented as seen under the magnifier. 



Position and locality. In the upper green shale of the Clinton group, associated with 

 Atrypa hemispherica and Leptcena corrugata. 



667. 5. CERAURUS INSIGNIS. 



Pl. a LXVI. Fig. 4. 



Cheirurus insignis. Beyrich, Ueber einige bcemische Trilobiten, Berlin, 1845. 

 See page 306 of this volume. 



The discovery of the fragment figured on this plate was the first indication I had of the 

 existence of this genus in the upper silurian strata. The imperfect heads of two other individuals, 

 from the shale of the Niagara group, have since been obtained. 



