RAYMOND: NEW AND OLD SILURIAN TRILOBITES, 21 
used the same name. When he came to figure a Wisconsin specimen, 
however, he proposed a new specific name for it, and the name was so 
obviously suggested by the Wisconsin specimens that I agree with 
Weller that those specimens should be considered the types of B. ioxus. 
Professor Weller has suggested that the specimens from New York 
may belong to another species. I have investigated the point as fully 
as the material at my command would permit, and have not so far 
been able to find any really good characteristics on which to base a 
separation. The best specimens from New York are usually small, 
and considerably flattened. The study of better material will prob- 
ably reveal characteristics not now evident, and I have therefore 
omitted from the synonymy the references to the New York specimens. 
Hall figured a pygidium which he assigned to the species, undoubt- 
edly correctly, but up to the present the thorax has been unknown. 
The M. C. Z. (Day collection), contains a large specimen, whose label 
states that it is the “only perfect specimen found at Racine.” It is 
not exactly a perfect specimen, though it retains cephalon, parts of ten 
thoracic segments and the pygidium. The axial lobe of the thorax 
is somewhat less wide than one would have expected from the large 
size of the animal, but, being 62% of the total width, is about the 
general average among the bumastids. The pygidium does not show 
an actual concave border, but there is a very decided flattening of the 
curve of the profile at the back. 
As the specimen is preserved, the pygidium is somewhat unnaturally 
drawn in, so that the actual length is not shown. On the other hand, 
the last thoracic segment is displaced from the others and there is a 
considerable space between the thorax and cephalon at the anterior 
end, and between the thorax and pygidium behind. The length of 
this specimen, therefore, gives only a rough approximation of the 
correct length. Incidentally it should be noted that the cephalon of 
this species has a large median tubercle near the posterior margin. 
It is shown in Hall’s figure, but omitted from. Weller’s. 
Measurements: — Length, about 180 mm.; cephalon 75 mm. long, 
110 mm. wide; thorax about 75 mm. long, about 100 mm. wide at 
middle, axial lobe 62 mm. wide; pygidium 65 mm. long, 102 mm. wide. 
A well-preserved pygidium is 68 mm. long and 100 mm. wide. 
Formation and locality: — Hall mentions Waukesha and Wauwa- 
tosa as localities for this species, but in very extensive collections from 
these places no specimens of this species are present, while we have a 
number of specimens from the Racine dolomite at Racine, Wisc. 
