36 Annals of the Carnegie Museum. 



toward the front and reaches the anterior margin, the form of the hypo- 

 stoma, and the absence of spines at the genal angles. In all these points 

 (except in the form of the hypostoma) Isoteloides is unlike Asaphus. 



Fig. I. Isotelus gigas Dekay. Outline drawing of young specimen, for com- 

 parison with fig. 4. 



Fig. 2. Asaphus expansus (Linne). Compare proportions of cephalon and 

 shape of glabella with i and 4. 



Fig. 3. Asaphus expansus (Linne). Side view of an enrolled specimen. Notice 

 the lack of a concave border round the cephalon and pygidium. 2 and 3 after Salter. 



Fig. 4. Isoteloides whilfieldi Raymond. Outline drawing of a specimen in 

 the Carnegie Museum. 



Isoteloides agrees with Isotelus in having the dorsal furrows and neck 

 ring very faint on the cephalon, in the almost entire absence of segmenta- 

 tion on the pygidium, in having a depressed border on the pygidium, and 

 in the presence of spines at the genal angles. It differs from Isotelus in the 

 form of the hypostoma, in having a defined glabella and a median tubercle, 

 and in having a narrow axial lobe. 



Isotelus angusticaudus Raymond of the Chazy and Asaphus homalno- 

 toides Walcott of the Black River and Trenton appear to belong to this 

 genus. 



Isoteloides whitfieldi nomen nov. 

 Plate XIV, figures 1-4. 

 Asaphus canalis Whitfield, Bulletin American Museum Natural History, I, 1886, 



336, pi. 34. figs. x-8. (not of Conrad or Hall). — Whitfield, Bulletin American 



Museum Natural History, II, 1889, 64, pis. 11, 12. 

 Not Asaphus or Isotelus canalis of Conrad, Hall, Billings, Clarke, Cleland, or 



Weller. 



The first mention of the specific name canalis as applied to an Asaphid 

 was by Hall in the "Paleontology of New York," Vol. I, p. 25. Hall 



