114 THE ROYAL SOCIETY OF CANADA 
Niobe, Onchometopus, Ogygites, Isotelus, and Homoglossa are present. 
In E, (Lower Trenton), /sotelus occurs. In F1, F2, (Richmond), 
Brachyaspis is the only genus. The correlations of the strata here 
given for Russia and Norway are those adopted by Bassler in his recent 
article on the Russian Bryozoa. 
It will be noted that in Europe, as in America, the Asaphide with 
entire hypostomas are most numerous in the Cambrian, but that they 
range rather higher in Norway and Russia than in America and the 
British Isles. There are several genera of asaphids which are present 
in Europe which are unknown or very raie in America. In the Baltic 
region, Asaphus, Pseudasaphus, Ptychopyge, Megalaspis, and Niobe 
are represented by many species, and of these genera only Megalaspis 
is now known in America, and of that genus only two very rare species 
have so far been described. 
The Genus Asaphus. 
Brongniart, the first systematic writer upon trilobites, was the 
author of the genus Asaphus, which is, therefore one of the first founded 
of the genera. Although a great variety of species have been referred 
to Asaphus, Asaphus expansus has remained the central type of the 
genus, and in Europe various genera and subgenera have been proposed, 
so that no such heterogeneous assemblage of species has been gathered 
under the genus as in America. 
Asaphus expansus is characterized by its short, broad cephalon 
and pygidium, from which all depressed borders are absent, by the 
rather prominent glabella which expands toward the front and reaches 
the anterior margin, the large prominent eyes, the course of the anterior 
portions of the facial suture, which meet in a point in front of the eye, 
and the short pygidium, with narrow well-defined axial lobe and smooth 
pleural lobes. 
Lines of Development from Asaphus. 
The genus as exemplified by the type-species is well developed in 
the Baltic region, and numerous species having the above generic charac- 
ters have been described, most of them from the Ordovician of the Bal- 
tic provinces of Russia. The variation seen among the described species 
is in the direction of the obliteration of furrows on the surface, that is, 
a further loss of evidences of original segmentation in cephalon and 
pygidium. Along with this there is a tendency to widen the axial lobe 
of the thorax, due, probably, to the greater development of the gnatho- 
bases of the coxopodites of the ambulatory appendages in the adaptation 
