NIAGARA FALLS AND VICINITY 



223 



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Fig. 154 Illaenus ioxus 



at all marked in either. Glabella smooth, indistinct, eyes large, 

 round, lateral cheeks small. Thorax usually consisting of 10 seg- 

 ments, with smooth pleurae. 



Illaenus ioxus Hall (Fig. 154). Bu- /' \ 



mastis barriensis Hall (1852. 



Pal. X. Y. 2 1302, pi. 66) 



Distinguishing characters. Elongate 



elliptic form; rounded, nearly equal 



cephalon and pygidium, with the triloba- 



tion scarcely marked; large eyes near the 



posterior lateral border of the cephalon; 



faint trilobation of thorax with very 



broad central lobe; granulose or punc- 

 tate surface. 



Found in the Clinton limestone lenses 



in great abundance, usually represented 



only by cephala and pygidia. These 



are often crowded together in great profusion to the exclusion of 



nearly every other fossil. Also found 

 rarely in the lower and middle Roches- 

 ter shale at Niagara. Also found at 

 Lockport and elsewhere (Hall). 



Genus dalmanites Barrande 



[Ety. : proper name] 



(1852. Systemc siluricn Boh. v. 1) 



Cephalon distinctly trilobate, with a 

 large glabella and prolonged lateral or 

 genal spines; glabella tumid, widest in 

 front, and divided by three well marked 

 lateral furrows; facial suture extending 

 from in front of the genal angles in- 

 ward to the eyes and thence forward 

 around the glabella; eyes large, with 

 numerous distinct lenses. Thorax of 

 11 segments with grooved pleurae. 

 Pygidium large, of many segments, 



triangular and often pointed or extended into a mucronate 



termination. 





Fig. 155 Dalmanites limulurus 



