Raymond: Notks ox Okdovician Tkii,oi!ITEs. 65 



is represented as wider than it really is, the correct proportions being 

 given in the text. 



Pygidiuni two-thirds as long as wide, uniformly convex, without chan- 

 neled border. Axial lobe broad at the anterior end, tapering rapidly, and 

 becoming obscure on the middle of the pygidium. On the cast it is more 

 prominent. There are no traces of segments on the axial lobe or on the 

 pleura. 



Locality. — This species is most common in the upper part of the Chazy, 

 but it has been found in all portions. Specimens have been obtained at 

 Crown Point, Valcour Island, Plattsburgh, and Chazy, New York, and 

 on Isle La Motte, Vermont. 



Genus IsOTELUS Dekay. 



Isotelus harrisi Raymond. 



Plate XVII, figure i. 



Isotelus harrisi 'Raymond, Annals Carnegie Museum, III, 1905, 343, pi. 12, figs. 3, 

 5-7; not fig. 4. — ScHMroT, Memoirs of the Imperial Academy of Sciences of 

 St. Petersburg, XX, 1907, 75. 



Specimens of Isotelus are abundant in the collection made by Prof. 

 Perkins, and it appears that there are two species in the bufT dolomite of 

 the reef at the base of the Upper Chazy. The cranidium figured on Plate 

 XII, figure 4, of my previous paper does not belong to Isotelus harrisi, but 

 to a new species which is described in this paper. The cranidium of 



Fig. 2. Upper figure. Isotelus platymarginatus. Lower figure. Isotelus 

 harrisi. Profiles of pygidia of the two species, one-half natural size, to show the 

 much wider border of /. platymarginatus. 



Isotelus harrisi has a short broad form, is very wide between the eyes, and 

 the eyes are situated far forward. The portion of the cranidium in front 

 of the eyes is evenly convex, and not depressed as in the new species. The 

 pygidium of /. harrisi is also wider in proportion to the length than in I. 

 platymarginatus, the concave margin is narrower, and the posterior end 

 of the axial lobe is much more prominent. The cephalon of this species 



