DESCRIPTION OF SOME NEW ASAPHID^E 
47 
The species seems to be somewhat common in the Lorraine 
at Toronto, and through the courtesy of Dr. W. A. Parks, the 
writer was permitted to study the series of very fine specimens 
in the Museum of the University of Toronto. Many of the 
specimens are very large. The largest complete specimen is 
285 mm, (nearly one foot) long, but there is another incomplete 
specimen whose measurements are all 10 per cent greater. 
All the specimens which were well enough preserved show 
spines at the genal angles of the cephalon. The spines are 
somewhat longer in the smaller specimens, but as they are usu- 
ally imperfectly preserved, no very satisfactory measurements 
could be made. 
On a specimen 145 mm. long, the spines were 17 mm. long,* 
on another, 171 mm. long, the spines were 31 mm. long; and on 
one 187 mm. long, the spines were 16 mm. long. The width 
of the axial lobe, in relation to the total width of the thorax 
at the back of the fourth segment, was measured in 15 speci- 
mens, and it was found that this ratio varied from 0*34 to 0 * 40, 
but that most of the specimens were near 0 * 37 and 0 * 38. As the 
writer has already pointed out, following various other writers, 
there is no real reason why this species should be confused 
with Isotelus gigas } the cephalon and pygidium always being 
shorter and wider, more rounded in outline, the axial lobe 
narrower, and genal spines being present in adults. 
Genus Brachyaspis, Sai/ter. 
Brachyaspis altilis, Raymond. 
Plate IV, figs. 3 and 7. 
This name was proposed without a formal description, in a pa- 
per on 44 Parallelism among the Asaphidse” in the Transactions of 
the Royal Society of Canada, Vol. V, 1912. The type is the 
specimen figured by Billings as Asaphus platycephalus in the 
44 Catalogue of the Silurian Fossils of Anticosti,” page 26, fig. 
9b. It differs from B . alacer (see Plate III, figure 6) 
principally in the character noted by Billings, that is, in the 
greater prominence of the eyes. The axial lobe of the thorax 
is also wider. Indeed, the axial lobe in B . alacer is very narrow 
