244 THE CANADIAN NATURALIST. [Vol. vi. 



uneven surface. They form long ridges running nearly parallel 

 to the coast, or north-east- and south-west, with intervening longi- 

 tudinal valleys excavated in the softer beds. One of these ridges 

 forms the long reef off Cacouna, which is bare only at low tide ; 

 another, running close to the shore, supports the village of Ca- 

 couna ; another forms the point which is terminated by the pier ; 

 a fourth rises into Mount Pilote ; and a fifth stretches behind 

 the town of Itiviere-du-Loup. 



The depressions between these ridges are occupied with Post- 

 pliocene deposits, not so regular and uniform in their arrange- 

 ment as the corresponding beds in the great plains higher up the 

 St. Lawrence^ but still presenting a more or less definite order of 

 succession. The oldest member of the deposit is a tough Boulder- 

 clay, its cement formed of gray or reddish mud derived from the 

 waste of the shales of the Quebec group, and the stones and 

 boulders with which it is filled partly derived from the harder 

 members of that group, and partly from the Laurentian hills on 

 the opposite or northern side of the river, here more than twenty 

 miles distant. The thickness of this Boulder-clay is, no doubt, 

 very variable, but does not appear to be so great as farther to 

 the eastward. 



Above the Boulder-clay is a tough clay with fewer stones, and 

 above this a more sandy Boulder-clay, containing numerous 

 boulders, overlaid by several feet of stratified sandy clay without 

 boulders ; while on the sides of the ridges, and at some places near 

 the present shore, there are beds and terraces of sand and gravel, 

 constituting old shingle beaches apparently much more recent 

 than the other deposits. 



All these deposits are more or less fossiliferous. The lower 

 • Boulderclay contains large and fine specimens o? Leda truncata 

 and other deep-water and mud-dwelling shells, with the valves 

 attached. The upper Boulder-clay is remarkably rich in shells 

 of numerous species ; and its stones are covered with Polyzoa and 

 great Acorn-shells (Balanus Ilameri)^ sometimes two iuches in 

 diameter and three inches hiirh. The stratified 2:ravel holds a 

 few littoral and sub-littoral shells, which also occur in some 

 places in the more recent gravel. On the surface of some of the 

 terraces are considerable deposits of large shells of il^a truncata, 

 but these are modern, and are the 'kitchen-middens' of the 

 Indians, who in former times encamped here. 



Numbers of Post-pliocene shells may be picked up along the 



