474 Correspondence. 



Their equivalence is not yet quite certain, but the strata are sup- 

 posed to be not far removed from A^ and A^. We shall call 

 this cHff A. The fossils from it are Tetradium 1, Or this 1 

 Lingula 2, Trilohites (genus undescribed) 1, with a great col- 

 lection of compound GraptoUdce, described and being described 

 by Mr. Hall under the genera GraptoUthus 25, Retiolites 1, 

 Reteograptus 2, Phyllograptus 5, Dendrograjptus 3, Thamnograp- 

 tus 3, Dictyonema, 3. 



I have given you these details of localities, because as the 

 subject requires further investigation we do not yet wish to 

 commit ourselves entirely as to the equivalency of separate exposures. 

 But there is no doubt that the whole is one group of strata 

 deposited under one set of alternating circumstances. The whole 

 fauna, as known up to the present time, is composed of — 



Articulata, 36 species. 



Mollusca, 55 " 



Graptolidae, . . ., 42 " 



Radiata, 4 " 



137 



Of this fauna not one species is found in the Anticosti group, 

 whf! e we have a gradual passage from the fauna of the Hudson 

 River formation to that of the Clinton, and not one of any forma- 

 tion higher than the Chazy. Mr. Billings recognises one species, 

 Madurea Atlantica (Bilhngs) as belonging to the Chazy, and 

 six species as belonging to the Calciferous. They are Lingula 

 Mantelli (Billings), Camerella undescribed, Ecculiomphalus 

 undescribed, Helicotoma uniangulata (Hall), H. perstriata (Bil- 

 lings), and one remarkable species of an undetermined genus, 

 like a very convex Cyrtodonta^ which occurs both at Mingan and 

 Point Levi. All of the forms, particularly the trilobites, remind 

 the observer of those figured by Mr. Dale Owen from the oldest 

 fossiliferous rocks of the Mississippi valley, while independent of 

 the six species identical with Chazy and Calciferous forms, there 

 are many others closely allied to those found in the latter formation 

 in Canada. 



From the physical structure alone no person would suspect the 

 break that must exist in the neighbourhood of Quebec, and without 

 the evidence of the fossils, every one would be authorized to deny it. 

 If there had been only one or two species of an ancient type, 

 your own doctrine of colonies might have explained the matter, 



