108 C. D. Walcott— Review of Br. R. W. Ells' s Report 



portions of the Quebec Group was based and with it went the 

 Crystalline Schist Group and the Yolcanic Group. The 

 former was referred to a pre-Cambrian Group, probably the 

 Huronian ; and the latter, to the Lower Cambrian. " Another 

 source of error, and possibly the most considerable," says Dr. 

 Ells, p. 43K, " was the assumption that the metamorphic rocks 

 of that area must of necessity be the equivalent of the un- 

 altered sediments of the St. Lawrence region, a theory which 

 once suggested, seems to have been unhesitatingly maintained, 

 although for its support, unnecessary inversions of strata, and 

 profound chemical changes were requisite." Dr. Selwyn also 

 pointed out the fact that sandstones, widely differing in age, 

 had been grouped under the Sillery series, and that the rocks 

 of the city of Quebec were cut off from the Lauzon red and 

 green slates by a fault and were not a portion of the Point 

 Levis series. 



Dr. Selwyn followed up his first paper with descriptive 

 notes, in 1882,* and a more popular article later in 1882. f A 

 still more recent paper sums up the results of the study of 

 the fossiliferous portion of the original Quebec Group.:): He 

 here states that no less than four distinct horizons can be re- 

 cognized, each of which is marked by a coarse band of con- 

 glomerate. Three of these bands, numbers 2, 3 and 4, are 

 fossiliferous limestone conglomerate, while one, number 1, is 

 chiefly feldspathic and dioritic, is non-fossiliferous and gener- 

 ally presents the appearance of a volcanic agglomerate or 

 breccia, which he considers pre Cambrian. Number 2 is in 

 the Sillery shales and is of Cambrian age, and contains exclu- 

 sively a fauna of Cambrian type. Number 3 is the celebrated 

 Point Levis conglomerate, and contains a pre-Cambriam and 

 Lower Cambro- Silurian fauna, while the fauna of the associ- 

 ated shaly bed is exclusively Lower Cambro-Silurian (Ordo- 

 vician). Number 4 is the Citadel Hill conglomerate of the 

 city of Quebec ; the fauna is mixed, but it is chiefly of Tren- 

 ton-Hudson age, as is that of the associated shales. The 

 mineralogical and lithological characters of the four groups 

 are markedly different, as are the paleontological features. 



Dr. Selwyn describes the structural geology, recognizing 

 the great fault and its branches, which have broken up the 

 formations in the vicinity of Quebec, and, also, the folds on 

 the Point Levis side which Sir William Logan mapped so 

 carefully in his study of the geology of this region. 



Dr. Ells's careful survey and mapping of the area embracing 

 the typical strata of the " Quebec Group," has demonstrated 



*Rep. Prog. Geol. Survey Cauada, 1880-'81-'82. 



f The Quebec Group Geology, Trans. Roy. Soc. Canada. 



\ Science, vol. ix, p. 267, 1887. 



