Of the Vicinity of Montreal. 405 



these deposits. The overlying sand is here of a light yellow 

 color ; the clay below very fine and unctuous, and of a grey colour. 

 Both contain a few large boulders, and are underlaid by boulder 

 clay, which toward the base of the mountain, comes up to the sur- 

 face. In some places the top of the clay is cut into deep 

 furrows filled by the sand, but in others the latter rests on an un- 

 broken surface, and a layer of greyish sandy clay forms a transi- 

 tion between them. The sand contains no shells. The thin 

 transition bed of sandy clay abounds in the following species, ar- 

 ranged as nearly as possible in the order of their relative abun- 

 dance : — 



Tellina Groenlandica. 

 Saxicava rugosa. 

 Mya arenaria. 

 Mytilus edulis. 

 Astarte Laurentiana. 

 Tellina calcarea. 

 Trichotropis borealis. 

 Fusus tornatus. 

 Bulla oryza. 

 Leda Portlandica. 

 In the clay below, very few shells occur; and these exclusively 

 Leda Portlandica and Astarte Laurentiana ; which are found prin- 

 cipally in its upper layers, and have their valves attached. Here 

 again we have evidence of a deep sea bed overlaid by one that is 

 littoral ; and it is also worthy of notice that the two species found 

 in the former are not now known as American shells, at least in 

 this latitude ; while those in the upper bed are common American 

 species. For convenience we may name the upper bed the Saxicava 

 Sand, and the lower the Leda Clay. (See Fig. 1.) 



At the cutting of the Montreal and Ottawa railway near St. 

 Denis street, and at the brick yards, the Leda clay and Saxicava 

 sand occur as before. From the latter of these places Sir W. 

 E. Logan has obtained a number of caudal vertebrae of a cetacean 

 and part of the pelvis of a seal, as well as fragments of wood of 

 the , common American cedar (Thuja occidentalis). These re- 

 mains were apparently contained in the Leda Clay. 



At the Mile End quarries, the limestone has in places a thin 

 coating of boulder clay, over which are stratified sand and gravel, 

 with layers of shells in the lower part. This place is on the sum- 

 mit of a slight ridge, and the thick fine clay of the brick-yard 



