454 TRANSACTIONS OF SECTION C. 
Columbia, perhaps as far as the Arctic Ocean. The remarkable feature of the 
life of the western province is its essentially American facies. 
Geologists are familiar with the triple classification of the Cambrian system 
by means of the trilobites in North America, as in Europe. The Lower Cam- 
brian division represents the Olenellus epoch of Walcott, characterised by some 
form of Olenellid, or, to use the name now given to the family by that investi- 
gator, the Mesonacide. ‘The western life-province contains the true Olenellus 
of which O. 7'hompsoni is the type. The strata yielding this fauna extend over 
such a wide area of North America that within this same province we find a 
western and an eastern facies. The western facies is found in Nevada and 
California, where Olenellus is represented by such specific forms as O. Gilberti 
and O. Freemonti. But it is noteworthy that these forms occur near the top of 
the Lower Cambrian series, and are soon followed by Zacunthoides and Crepice- 
phalus, trilobites of middle Cambrian affinities. Towards the lower part of the 
sequence of deposits, which there consist mainly of limestone, and extend down- 
wards for a distance of over 4,000 feet beneath the beds containing the true 
Olenellus, Walcott found specimens of Holmia Rowei and Nevadia Weeksi. 
The latter form is regarded by him as the most primitive of all the Mesonacide 
yet known. Near the base the limestones have yielded the primitive corals 
Archeocyathus and Lthmophyllum, and the brachiopods Mickwitzia and T'rema- 
tobolus. The other forms found on this horizon belong to the following genera : 
(trilobites) Protypus and Microdiscus, (brachiopods) Kutorgina, Swantonia, 
Nisusia, Billingselia, and (tubicolar annelids) Hyolithellus and Salterella. The 
eastern facies of the western life-province is best known from the region of 
Georgia, in Vermont. It is the home of the type species of Olenellus 
(O. Thompsoni). It is associated with Mesonacis vermontana, which has now 
given the name to the whole family, with Hiliptocephalus asaphoides, one of the 
earliest known trilobites of the family, and with other forms such as Bathy- 
notus, Holopygia, Protypus, and Microdiscus. The tubicolar worms are repre- 
sented by Hyolithellus and Salterella, the brachiopods by Nisusia, Swantonia, 
Kutorgina cingulata, and Paterina labradorica. There can be no doubt that 
the assemblage of organic remains found in this Georgian terrane is merely the 
counterpart of that found in the Olenedius zone of the North-West Highlands. 
Proceeding now to the eastern life-province, we find that the Lower Cam- 
brian rocks are characterised by the trilobite genus Callavia, belonging to the. 
family of the Mesonacide, and bearing a close resemblance both to Holmia and 
Nevadia. In Southern Newfoundland two species of Callavia occur, of which 
CU. Bréggeri is the type. It is accompanied by Microdiscus, Hyolithellus, 
Paterina labradorica, and Helenia bella. In New Brunswick the Protolenus 
fauna, with Protolenus as the characteristic trilobite, probably represents the 
upper part of the Olenedlus zone. In this connection the recent discovery of the 
Protolenus fauna by Mr. Cobbold, in Shropshire, in strata associated with 
Callavia, and overlain by beds yielding Paradowides, is of special importance, 
as it shows the close relation between the Lower Cambrian fauna of Wales and 
that of the Atlantic or eastern province of North America.° 
The Middle Cambrian division of the western life-province is characterised 
chiefly by the trilobite genus Olenoides; indeed, the western part of it is the 
home of Olenoides and the large tailed trilobites. The characteristic genera of 
this group to be found in that region are Kootenia, Zacanthoides, Bathyuriscus, 
Asaphiscus, Neolenus, Dorypygella, Dorypyge, Damesella, and Ogygopsis. 
In this region the Middle Cambrian limestones and shales occurring on 
Mount Stephen, in British Columbia, have yielded a magnificent series of trilo- 
bites, eurypterids, limuloids, crustacea ranging from congeners of the brine 
shrimps to phyllocarid nebalids, annelids belonging to most of the still extant 
families, holothurians, meduse, and other organic remains. For the most part 
many of these forms are so fragile that only their tracks remain as indications 
of their existence in paleozoic deposits. Not till we reach the Solenhofen slates 
in Jurassic time do we find similar favourable conditions for the entombment 
and preservation of their highly modified successors. The remarkable evidence 
bearing on the evolution of groups of organisms furnished by this assemblage of 
fossils from Mount Stephen has been admirably described and illustrated by 
* Quart. Jour, Geol. Soc., vol. |xvii., p. 296, 1911. 
