TRANSACTIONS OF SECTION C. 785 
term Archean to be applied to the Lower Laurentian gneiss, until it also shall 
have afforded some indications of the presence of life. 
He insisted on the duty of paleontologists to give more attention to the pre- 
Cambrian rocks, in the hope of discovering connecting links with the Cambrian, 
and of finding the oceanic members of the Huronian, and less metamorphosed equi- 
valents of the Upper Laurentian, and so of reaching backward to the actual 
beginning of life on our planet, should this prove to be attainable. 
2. Some Features of the Early Cambrian Faunas. By G. ¥. Matruew, 
D.Sc, F.RS.C. 
Trilobites. 
The larval features of the early Cambrian Trilobites are chiefly referred to in 
this paper because in them we may look for points of structure which will appear 
in the adult condition of their predecessors. 
The early Cambrian Brachiopoda and Ostrocoda are also briefly considered. 
Except in Olenellus and its allies the larval forms of the earliest trilobites are 
little known; but in those of the Paradoxides beds a number of them belonging to 
different genera are known, so that in these we have fuller data for comparison. 
The abundance and variety of trilobites in the Cambrian rocks are truly 
yemarkable; and the flexibility of the type is indicated by the numerous genera 
that appeared successively in that early age. They thus become valuable in 
marking the divisions of these rocks, as the vertebrates do those of the Tertiary ; 
and their remains enable us to recognise different parts of the Cambrian system 
with ease and certainty in all the regions around the Atlantic ocean. 
This being the case, it may be profitable to examine the forms of the earliest 
Cambrian trilobites, and note how they compare with the larve of the trilobites of 
the Paradoxides beds. The law of development would lead us to expect that in 
the pre-Paradoxides faunas of the Cambrian certain features of the larval forms of 
the trilobites of the Paradoxides beds should appear as permanent adult features 
in their predecessors. And such is the case. 
In 1892 Dr. J. Bergeron summed up the evidence on this point, derivable 
from the trilobites of the Paradoxides and Olenellus faunas, in his article, “ Is the 
fauna called primordial the most ancient fauna’ ”! He utilised the studies of 
Barrande, Walcott, Ford, and others for this purpose, and his conclusion was that 
there must have been a more ancient fauna. 
Discoveries of other faunas beside that of Olenellus, older than the Paradoxides 
beds, have been made since Bergeron wrote upon this subject, and we may now 
place his theory against some additional facts which bear upon it. 
To make the application clearer, the author briefly presented some of the 
characteristics of the earliest larval stages of the trilobites of the Paradoxides 
beds, as shown in the young of Paradoxides, Ptychoparia, Conccoryphe, Microdiscus, 
and Agnostus. Among them are the following :— 
1. Predominance of the cephalic over the caudal shield. 
2, A long narrow giabella, with nearly parallel sides. In these early moults 
the posterior lobes of the axial rachis (which includes the glabella) are short and 
weak,.as compared with the anterior, and especially the first.” 
3. The eyes are absent; when they first appear they are near the lateral 
margin, and in several genera are elongated. 
4, There are no movable cheeks; when these first appear they are narrow and 
marginal. 
5. There is no thorax; this region begins with one segment, and in some 
genera never exceeds the number of 2 to 4. The pleure at first are short. 
6. The pygidium at first is quite short and of one segment. 
1 Revue générale des Sciences, Paris, 1892. 
; * Paradoxides is apparently an exception to this rule, but we do not know“its 
earliest stages. y 
