180 



Faunas of the 

 St. John 

 terrane. 



Tremadoc 

 fauna. 



FAUNAS OF THE ST. JOHN TEREANE. 



As the faunas found in the St. John terrane in Cape Breton were not 

 separately of very many species, they are here described collectively > 

 with reference at the end of each species to the fauna to which they, 

 belong. 



While Brachiopods form the bulk of the Etcheminian fossils in Cape 

 Breton, Trilobites show in considerable abundance in some of the zones 

 of the St. John terrane, and are of varied types. The lower zones, so 

 far as this exploration went, did not produce many fossils, although at a 

 few places some forms of the Paradoxides fauna were found, and in places 

 the middle zones yield an abundance of the Inarticulate Brachiopods. 



The middle zones here, as in New Brunswick, abound in ripple-marked 

 beds filled with worm burrows, and bear other evidences of shallow-water 

 origin. These have a fauna of Atrematous Brachiopods that is quite 

 like that of the corresponding measures in New Brunswick. 



There is also similarly a return to deep water beds in the upper part 

 of the terrane, and with the dark gray shales of this portion, appear 

 faunas similar to those known from this part of the terrane in New 

 Brunswick. This part, though comparatively thin, has three Upper Cam- 

 brian faunas, so that it represents nearly as wide a period of time as 

 similar shales in New Brunswick. These three faunas are those of Pel- 

 tura, Dictyonema and Asaphellus. The latter being known in England 

 as the Tremadoc fauna. In the edition of Dana's Geology of 1875 this 

 group (the Tremadoc) is classed as Silurian (i. e. Ordovician). In the 

 later edition, 1896, it is transferred to the Cambrian. Prof. Jas. Hall 

 referred species of this fauna from the sandstones of the Mississippi valley 

 to the Potsdam (therefore Cambrian) in 1863? Mr. C. D. Walcott has 

 referred strata in the west of America and at Saratoga, N. "., holding this 

 fauna, to the Potsdam or Upper Cambrian. But in Europe the consensus 

 of opinion (omitting Great Britain) places this fauna in the Ordovician or 

 Lower Silurian. Lindstrbm says that in Sweden not one species passes 

 from the Cambrian to the Ceratopyge Fauna (i. e. the Tremadoc) while 

 nineteen species pass from the Ordovician to the Silurian (Upper). Four 

 species, however, are recorded as passing in Wales from the Lingula 

 Flags to the Tremadoc Group.* Elsewhere it is stated that 6 out of 37 

 species of Crustacea pass from the Tremadoc to the Arenig in Wales, f 

 So that it is difficult to draw a line of absolute division between Cambrian 

 and Ordovician, either above or below the Tremadoc. 



* Mem. Geol. Surv. G. B., vol. iii, p. 365, etc. 

 f Ibid. p. 353. 



