38 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
from the “Niagara” at Cicero, Illinois (M. C. Z. 629). A second 
specimen, tentatively referred to this species, is in the Museum of the 
Geological Survey of Canada, and is from the Guelph of Hespeler, 
Ontario. 
CHEIRURUS TARQUINIUS Billings. 
Cheirurus tarquinius Billings, Proc. Portland soc. nat. hist., 1863, 1, p. 121, 
pr. Ss, tee 
This is a little-known species of the Ch. insignis group. It has a 
short, wide cephalon, narrow triangular basal lobes on the glabella, a 
short frontal lobe, and the first two pairs of furrows turn backward, 
are quite straight, and are intermediate in length between those of 
Ch. niagarensis and Ch. welleri. The species is especially characterized 
by the forward position of the eyes, which are opposite the second 
glabellar lobes, and the consequent small free cheeks and long fixed 
cheeks. The genal angles appear to be spineless. 
The type is No. 3081 in the Museum of the Geological Survey of 
Canada. Associated with it is a pygidium from the same locality. 
It is of the znszgnis type, with three pairs of spines, but the median 
spine is shorter and more rounded than in either Ch. insignis or Ch. 
miagarensis. A poorly preserved hypostoma in the same collection 
has the posterior end more rounded than that of Ch. niagarensis, and 
thus more like that of Ch. wellert. 
Measurements: — The type (G. S. C. 3081) is 19 mm. long, 35 mm. 
wide; and the glabella is 12 mm. wide at the neck-ring and 17 mm. 
wide at the frontal lobe. 
Formation and locality: — Middle Silurian at Port Daniel, Bay, 
Chaleur, P. Q., Canada. Also reported by Billings from Masardis, 
Maine. 
CHEIRURUS HYDEI (Weller). 
Ceraurus hydei Weller, Bull. Chicago acad. sci., 1907, no. 4, pt. 2, p. 264, pl. 24, 
i ee 
This species is of more than ordinary interest, from its resemblance 
to a Ceraurus. The cephalon and thorax are those of a typical 
Cheirurus, but the pygidium is that of Ceraurus. This at once raises 
the question as to whether this is a Cheirurus which has developed a 
Ceraurus-like pygidium, or whether it is a Ceraurus whose cephalon 
and thorax have developed in a manner paralleling that of Cheirurus. 
