68 Annals of the Carnegie Museum. 



homalnotoides (Walcott) and the species here described are not exactly 

 similar to the type- species, but they seem to fit in this genus better than 

 in Isotelus. The hypostoma figured is thought from the association to 

 belong to /. angusticaudus, and its hemispheric body is certainly much 

 like that of the type of the genus. 



Isoteloides angusticaudus Raymond. 



Plate XVII, figure 7; Plate XVIII, figure i; Plate XIX, figure 8. 

 Isotelus angusticaudus Raymond, Annals Carnegie Museum, III, 1905, 345, pi. 13, 

 figs. 3. 4- 



An entire specimen and a good cephalon of this species were obtained 

 by Professor Perkins. The species was originally described from the 

 pygidium. 



Description. 



Entire animal oval, somewhat pointed at the extremities, about twice as 

 long as broad. Bodj^ compressed, strongly convex; shell finely punctate. 



Cephalon about three-quarters as long as wide, strongly convex, de- 

 pressed and rather pointed at the anterior margin. Eyes large, about 

 their own width from the posterior margin. Glabella nearly smooth, the 

 cast showing two pairs of very faint furrows. Genal angles rounded, 

 without spines. The neck-furrow is slightly impressed, and in front of it 

 is a small median pustule. 



Thorax of eight segments. Axial lobe rather broad for this genus; 

 pleura abruptly deflected. 



Pygidium narrow, strongly and uniformly convex, tapering rapidly. 

 Sides nearly straight, the margin slightly concave and very steep; axial 

 lobe not strongly defined, wide at the anterior end, but tapering rapidly. 

 In the cast there are traces of annulations on the axis and faint indications 

 of ribs on the pleura. 



The entire specimen is 58 mm. long, and 27 mm. wide. One pygidium 

 is 18 mm. long and 19 mm. wide, while a large one is 35 mm. long and 36 

 mm. wide. A large cephalon is 35 mm. long and 50 mm. wide. 



This species differs from all other AsaphidcB in the Chazy in its long 

 narrow form. It is very closely related to Isoteloides homalnotoides (Wal- 

 cott) of the Trenton, but that species seems to have a more strongly 

 defined glabella and smaller eyes. 



Locality. — Isoteloides angusticaudus is a rare fossil on Valcour Island, 

 New York, but is common in the buff dolomite of the reef on Isle La 

 Motte, Vermont. 



