84 THE ROYAL SOCIETY OF CANADA 



The basal Palseozioc terranes of Cape Breton are those which 

 have yielded a profusion of early and primitive forms of the Brachio- 

 poda and Ostracoda. These two classes of marine animals have left 

 remains even in the few seams of shale that are intercalated with the 

 oldest masses of volcanic ashes and scoria that were thrown out along 

 the margin of the Cambrian sea in the region of Cape Breton and 

 when we consider the diversity of the genera in these deposits, it is 

 clear that we are dealing with a marine fauna already of considerable 

 complexity.* 



But the fauna these beds contain is so closely linked with that 

 of the stratified rocks that overlie these volcanics, that the two are 

 evidently parts of a consecutive series of measures of nearly the same 

 geological age. 



These two groups of marine animals show in some measure the 

 types present in Cape Breton in this natal time of the Palaeozoic 

 faunas, so far as they can be recognized by their hard parts, preserved 

 in the fine mud in which they were entombed. The remains so far 

 observed belong to two classes of the animal kingdom, Crustacea and 

 Brachiopoda. Of the former only one order, the Ostracoda, is 

 represented and the species are of comparatively large size (Escasona ? 

 and Indiana) . 



But there is a more varied representation of the Brachiopoda, 

 in two of its divisions, that with sliding valves (Lingulella, Lingulepis, 

 and Leptobolus) and that with a perforate beak to the ventral valve 

 (Acrothyra and Acrotreta. All these were of genera which shewed a 

 fuller development in the succeeding (Etcheminian) fauna. 



But though so imperfectly represented in the Coldbrook terrane, 

 these scanty remains show that the early Palaeozoic species were 

 present in the neighboring seas, awaiting an opportunity to develop 

 their genera at those near-by shores, when the physical conditions 

 should have made it possible. 



We have found no trace of trilobites in the stratified marine beds 

 of the Coldbrook terrane, but a species has been recognized in the 

 uppermost assize of the overlying Etcheminian, in a primitive type 

 referred to the genus Solenopleura.\ 



Neither in the Coldbrook terrane nor in the lower half of the 

 Etcheminian, have we found any examples of the genus Acrothele, 



*Geol. Surv. of Canada. Report on the Cambrian rocks of Cape Breton, 1903. 

 Coldbrook terrane pp. 12, 71, 73. 



tReferred to this genus on account of the general form of the headshield, but 

 the eyelobe is too long and the marginal fold too wide and too heavy to accord with 

 the type of this genus. 



