No 3.] DAWSON — POST-PLIOCENE. 245 



shores of the two little bays between Cacoima and Riviere-du- 

 Loup ; but I found the most prolific locality to be on the banks 

 of a little stream called the Petite Riviere-du-Loup, w^hich runs 

 between the ridge behind Cacouna and that of Mount Pilote, and 

 empties into the bay between Riviere-du-Loup and the pier. In 

 these localities I collected and noticed in my paper on this place '^ 

 more than eighty species, about thirty-six of them not previously 

 published as occurring in the Post-pliocene of Canada. 



We have thus at Rivi(>re-du-Loup indubitable evidence of a 

 marine Boulder-clay, and this underlies the representative of the 

 Leda clay, and rests immediately on striated rock surfjices — the 

 striae running north-east and south-west. 



The Cacouna Boulder-clay is a somewhat deep-water deposit. 

 Its most abundant shells are Leda truncata, Nucula tenuis, and 

 Telllna proxima, and these are imbedded in the clay with the 

 valves closed, and in as perfect condition as if the animals still 

 inhabited them. At the time when they lived, the Cacouna 

 ridges must have been reefs in a deep sea. Even Mount Pilote 

 has huge Laurentian boulders high up on its sides, in evidence 

 of this. The shales of the Quebec group were being wasted by 

 the waves and currents ; and while there is evidence that much 

 of the fine mud worn from them was drifted far to the south- 

 west to form the clays of the Canadian plains, other portions 

 were deposited between the ridges, along with boulders dropped 

 from the ice which drifted from the Laurentian shore to the 

 north. The process was slow and quiet ; so much so that in its 

 later stages many of the boulders became encrusted with the cal- 

 careous cells of marine animals before they became buried in the 

 clay. No other explanation can, I believe, be given of this de- 

 posit ; and it presents a clear and convincing illustration, applic- 

 able to wide areas in Eastern America, of the mode of deposit of 

 the Boulder-clay. 



A similar process, though probably on a much scalier scale, is 

 now going on in the Gulf. Admiral Bayfield has w^ell illustrated 

 the fact that the ice now raises, and drops in new places, multi- 

 ■ tudes of boulders, and I have noticed the frequent occurrence of 

 this at present on the coast of Nova Scotia. At Cacouna itself, 

 there is, on some parts of the shore, a band of large Laurentian 

 boulders between half tide and low-water mark, which are moved 



* Canadian Naturalist^ April, 18C5, 



