590 [April 2. 



inclined grauwacke and slate ; but, on the other hand, it must be 

 remarked that it has never, as far as we know, been found over- 

 lying the latter unconformably, although sandstone or conglomerate 

 is occasionally interposed between it and the granite or gneiss, as 

 among the Thousand Islands, and on the rivers St. Maurice and 

 Montmorenci. 



The northern shore of the St. Lawrence River and Gulf, from 

 Cape Tourment, ten leagues below Quebec, eastward to the Min- 

 gan Islands, is composed of primary rocks ; the limestone and the 

 grauwacke which form the islands and southern shore of the 

 river, appearing in immediate contact with them only at St. Paul's 

 and Murray Bays, and, more extensively, on Lake St. John, up 

 the Saguenay River, as already mentioned. 



For a more particular description of the primary rocks of this 

 coast, and also of the Mingan Islands, with their raised beaches, 

 limestone columns, &c., I must refer to a paper read before the Geo- 

 logical Society in 1833, and printed in their Transactions* which 

 Avas accompanied by specimens of the fossils which I have now 

 added to, and which have been examined by M. de Verneuil, to whom 

 I am indebted for their specific names, and many valuable remarks 

 respecting them. On this occasion it will be sufficient to state, 

 that the Mingan Islands extend for about fifty miles along the 

 north coast of the Gulf of St. Lawrence, opposite the great Island 

 of Anticosti, from which, at the nearest point, they are distant 

 about nine miles. None of them are more than three miles distant 

 from the main land, where the limestone may be seen at various 

 points resting immediately on granitic rocks. 



The Mingan Islands are entirely composed of limestone, having a 

 slight dip to the southward. So also is the Island of Anticosti, which, 

 from its relative position to the southward, and similar dip, may 

 be expected to be higher up in the Silurian series. The limestone 

 of these islands resembles that of Lake Huron, in being very nearly 

 horizontal ; although there is a slight dip, which, continued for many 

 miles, must give a very considerable thickness to the whole range, 

 measuring from the lower beds that rest on the granite of the main- 

 land to those that dip gradually beneath the sea on the southern" 

 coast of Anticosti, or form the summits of the unvisited ridges of 

 the interior of the island, five or six hundred feet above the sea. 



The following are the most abundant fossils of the islands of 

 Mingan : — 



1. Illoenus crassicauda. 5. Terebratula plicatella (not Sow.). 



2. Orthoceras duplex. 6. Euermis ? 



3. Orthoceras annulatus. 7. Leptana Humboldtii. 



4. Euomphalus. 8. Pleurotomaria. 



And of the Island of Anticosti : — 



1 . Spirifer lynx (Eichwald), var. 2. Orthis, allied to O. elegantula. 

 of S. biforatus (Schlotheim). 3. Leptaena Humboldtii ( De Vern.). 



* Geol. Tr. 2d Ser. vol, v. p. 89. 



