MINERALS AND GEOLOGY OF CANADA, 31 
The reader will find descriptions of various 
fragmentary species in papers by Mr. Billings in 
the fourth and fifth volumes of the Canadian 
Naturalist. He is referred also to that publi- 
cation for figures of less known or uncertain 
species of Jl/cenus and other forms of this 
order. 
Ceraurus.—This genus is the Cheirurus of 
European authors. It is more or less closely 
allied to Dalmannites, but the eyes exhibit only 
a delicate reticulation, and the pleure have a 
raised band on the surface, in place of a groove 
as in the latter type. The glabella is large, and furrowed at the 
sides. The facial suture cuts the side of the head-shield. The angles 
of the head terminate in points or horns. The pleure are also 
pointed ; and the caudal shield has a spinose or serrated outline, 
or otherwise terminates in one or several horns. Body-rings eleven 
in number. The genus ranges from Lower Silurian into Devonian 
beds. A common species from the Trenton Group, Ceraurus pleurex- 
anthemuus, is shewn in fig. 146. Impressions of the glabella, and 
of the two-horned pygidium, are especially abundant. 
Fig. 145. 
HGS 
Fig. 146. Fig, 147. 
Oalymene.—The glabella of this genus is prominently developed, 
lobed, and contracted anteriorly. The head-angles are rounded, and 
the facial suture cuts these. The body-rings are thirteen in num- 
ber: pleurze rounded. Pygidium with entire outline. Our most 
common species is the widely distributed C. Blumenbachii (fig. 147). 
This species ranges from the Trenton Group into the Middle Silurian 
deposits. It is very frequently found in a “rolled up” condition. 
