3i6 



NORTH AMERICAN INDEX FOSSILS. 



the cheeks; anterior to the first glabellar lobe it is longer, wider 

 and more abruptly rounded than in C. callicephala and C. senaria. 

 Thorax with side lobes flattened on top for about a third of the 

 length of the pleura and then bent abruptly downward; segments 

 arch forward on the axis, each bearing a rounded node just within 

 the dorsal furrows. The pleura of the pygidium are also more 

 flattened than in the first two species and terminate within the 

 marginal border. The entire pygidium is larger and is promi- 



FlG. 1629. Calymene platys, X Vl- (After Hall.) 



nently set off from the thorax by its very abrupt inflection and by 

 its ornamentation. 



Niagaran throughout central and eastern North America ; Guelph 

 of New York, Ohio and Ontario. 



158. C. platys Green. (Fig. 1629.) Devonic. 



Very large. Hypostoma subquadrate, with a notch on each of 

 the four sides. Pygidium truncate and emarginate on the posterior 

 border. 



Onondaga of New York and Indiana. 



LXII. HoMALONOTUs Kocuig. 



Large and indistinctly trilobed owing to the obsolescence of the 

 longitudinal furrows. Cephalon wider than long, somewhat pointed 

 anteriorly and with rounded genal angles. Glabella nearly quad- 

 rate, nearly smooth, or very faintly furrowed. Eyes small. Thorax 

 of 13 segments. Pygidium triangular and smaller than the ceph- 

 alon. Facial sutures shown in Fig. 1631. Ordovicic-Devonic. 



