RAYMOND: NEW AND OLD SILURIAN TRILOBITES. 41 
CHEIRURUS NUPERUS Billings. 
Cheirurus nuperus Billings, Cat. Silurian fossils Anticosti, 1866, p. 60, f. 20. 
This species was described from an isolated glabella and pygidium 
from Div. 3 at East Point, Anticosti. Schuchert and Twenhofel have 
listed it with a query from the upper part (D9) of their Gun River 
formation, where it is associated with Bilobites bilobus and Triplecia 
ortont, in strata of Clinton age. 
Like Ch. hydei, this species shows the Cheirurus type of basal lobes 
on the glabella and the pygidium shows three pairs of spines. The 
outer pair or great spines are large, flat and not so long or so much 
curved as in most of the species of the genus. C. hydei has the great 
spines much more slender and further apart than in C. nuperus. 
The type of this species is lost, and no further specimens have been 
described. 
SPHAEREXOCHUS ROMINGERI Hall. 
Sphaerexochus romingeri Hall, 20th Rept. N. Y. state cab. nat. hist., 1868, 
p. 375, pl. 21, f. 4-7. (See Weller, Bull. Chicago acad. sci., 1907, no. 4, 
pt. 2, p. 209, for earlier and later references to this species). 
This is an exceedingly common species in the Niagaran in the 
Chicago and Wisconsin areas but the pygidium is rare and usually 
incorrectly figured. Hall started the misrepresentation figuring the 
pygidium as having three spines on each side and a rounded projection 
at the back. 
As a matter of fact, the margin of the pygidium is entire, and the 
spines figured by Hall are the ribs on the pleural lobes. Weller 
produced practically a similar figure, and one of Kindle’s is about 
the same, but the other, being of a mould, is more correct. Other 
describers of the species have refrained from figuring the pygidium. 
