107 



The lower beds of the Grande Greve division are exposed 

 on the Kings road and carry an association of species 

 which is most distinctively indicative of the Oriskany 

 horizon ; such as Hipparionyx proximus, Rensselaeria ovoi- 

 des gaspensis, Spirifer arenosas, Chonostrophia complanata, 

 Rhipidomella musculosa, etc. The limestones carry much 

 nodular chert and in some places masses of silicious sponge 

 spicules constitute the basis of the rock.* 



Beneath the Grande Greve limestone lies a series of less 

 purely calcareous, more magnesian beds, with but few 

 fossils and these mostly diminutive forms, — a deposit 

 formed under impeded marine conditions in which life 

 was unable to flourish. These are the Bon Ami beds, 

 and they form a large portion of the cliff face of the river 

 escarpment. They can be examined on the face of Mt. 

 St. Alban at the summit of the Kings road and at Cape 

 Bon Ami, where a ladder down the face of the cliff at 

 the end of the Portage road makes them accessible and they 

 constitute the greater part of the bold front of Mt. St. 

 Alban. Such fossils as they contain are quite distinctively 

 of Helderberg age. 



Beneath and conformable to the Bon Ami beds are the 

 Si. Alban beds with a fauna quite exclusively identical 

 with the Helderberg (lowest Devonian) fauna of New 

 York. These calcareous compact shales are to be seen 

 in exposures along the shores of Cape-des-Rosiers cove 

 at the foot of Mt. St. Alban. About 50 species have been 

 identified from these rocks of which more than one half 

 are found in the lower divisions of the Helderberg series 

 in New York, while hardly more than one-fifth occur in 

 the Grande Greve limestones. Access to these exposures 

 requires the descent of the Kings road down the slope of 

 Mt. St. Alban and thence across the fields to the shore of 

 the St. Lawrence river. 



Sir William Logan estimated the thickness of these lime- 

 stones at 2,000 feet (610 m.) and of this the Grande Greve 

 beds include approximately 600 feet (180 m.). The 

 boundary, however, between the sub-divisions is not a 

 sharp one, but in all, the beds afford a total not paralleled 

 in the Devonian section at Perce. In fact the entire 

 series is wanting elsewhere and in all the other Gaspe 

 folds, so far as known, except so far as represented by the 



*The fauna of all these Devonian beds has been described in detail by Clarke. 



