No. 3.] DAWSON — POST-PLIOCENE. 249 



An interesting section of the deposits is that obtained at 

 Logan's Farm, which may be thus stated in descending order : 



ft. in. 



Soil and sand, 1 9 



Tough reddish clay, J 



Gray sand, a few specimens of Saxicava rngosa, Mytihis edulis, 

 Tellina Grocnlandica, and Mya arenaria, the valves generally 

 united, 8 



Tough reddish clay, a few shells oi Asiarte Laurentiana, and Leda 



truneata, 1 1 



Gray sand, containing detached valves of Saxicava riigosa, Mya 

 truneata, and Tellina Grcenlandica : also Trichotropis bore- 

 aiis, and Balanus crenatus ; the shells, in three thin layers, 8 



Sand and clay, Avith a few shells, principally Saxicava in de- 

 tached valves 1 3 



Band of sandy clay, full of Natlca claiisa, Trichotropis borealis, 

 Fusus tornatus, Buccinun glaciale, Asiarte Laurentiana, 

 Balanus crenatus. «fec.&c., sponges and Foraminifera. Nearly 

 all the rare and deep-sea shells of this locality occur in this 

 band, 3 



Sand and clay, a few shells of Astarte and Saxicava, and remains 



of sea-weeds with Lepralia attached ; also Foraminifera,. . . 2 



Stony clay (Boulder-clay). Depth unknown. 



In this section the greater part of the thickness corresponds to 

 the Leda chiy, which at this place is thinner and more fossiliferous 

 than usuaL Along the south-east side of the Mountain, and in 

 the city of Montreal, the beds have been exposed in a great num- 

 ber of places, and are in the aggregate at least 100 feet thick, 

 though the thickness is evidently very variable. The succession 

 may be stated as follows : 



1. Saxicava Sand. — Fine uniformly grained yellowish and gray 



silicious sand with occasional beds of gravel in some 

 places, and a few large Laurentian boulders, Saxicava, 

 Mjjtilus, &c., in the lower part. Thickness variable, in 

 some places 10 feet or more. 



2. Leda Clay. — Unctuous gray and reddish calcareous clay, 



which can be observed to be arranged in layers varying 

 slightly in colour and texture. Some of these layers have 

 sandy partings in which are usually Foraminifera and 

 shells or fragments of shells. In the clay itself the only 

 shells usually found are Leda truneata and a smooth 

 deep-water form of Tellina Groenlandica ; but toward the 



