DESCRIPTION OP SOME NEW ASAPHID® 
45 
near the same horizon and locality as the specimen collected 
by Mr, Ingall. 
Locality . — The specimen figured was collected by Mr. Elfric 
Drew Ingall from a layer of limestone within 15 feet above the 
top of the Trenton on Adeline street, between Preston and 
Rochester streets, Ottawa, Ontario. The horizon is the lower 
part of the Collingwood formation, supposed to be of early 
Utica age. The specimen is No. 7817. 
Genus Isotelus, Dekay 
ISOTELUS LATTJS, SP. NOV. 
Plate 5. 
In the Trenton at Ottawa there is a species of Isotelus which 
differs from J. gigas in having all its parts much wider. As 
the type I have selected the specimen figured in the Geology of 
Canada, 1863, p. 184, figure 183, as Asaphus platycephalus. 
This figure has been so frequently copied in text books, that 
the species, though new, has long been well known. Another 
well known specimen of this species is the one on which append- 
ages were found by Billings. 
Description. 
Body oval in outline, a little more than one-half longer than 
wide, broadly rounded at both extremities. Dorsal surface 
relatively smooth, the axial lobe of the thorax wide, and the 
whole test less convex than in I. gigas. The test is punctate, 
and is marked by wavy, inosculating depressed lines. 
Cephalon three-fourths as long as wide, regularly curved in 
front, depressed convex, dorsal furrows obsolete, thus leaving 
the glabella undefined. Eyes relatively small, far apart, situ- 
ated more than their own length from the posterior margin of 
the cephalon. Genal angles rounded in the adult. Young 
unknown. * 
Pygidium shorter and more nearly semi-circular than the 
cephalon, smooth, with depressed border of medium width. 
Dorsal furrows obsolete, and axial lobe not defined. 
