in some of our Post Tertiary Deposits* 43 



brick yard, I received a fine specimen of Limncea umhrosa, Say, 

 from Sir Wm. Logan, -who obtained it from the tbin bed of 

 sand at the same locality. A Cyclas and L. umhrosa were 

 found by Dr. Dawson amongst marine shells thrown out of a 

 ditch on Logan's Farm.* I have collected specimens of the latter 

 at the same place and believe them to be contemporaneous with 

 the marine shells. 



I might mention that the ponds on the highest part of Mon- 

 treal Mountain, about 700 feet above the level of the sea, teem with 

 Limncea umhrosa and L. caperata^ besides numerous other species 

 of our common fresh water Gasteropods. Ponds, with all these 

 species living in them, may have existed in the same situation 

 when Montreal Mountain was an island in the sea which covered 

 the surrounding plain, and from them the rills running down 

 its sides may have carried the specimens found in the sand which 

 was then being deposited around its base. 



Green's Creek. 



Green's Creek enters the Ottawa in the Township of Gloucester, 

 on the south side, about ten miles below Ottawa City. Here, 

 the Leda clay has aflforded a larger number and more interesting 

 variety of fossils than at any other locality. At low water, which 

 is generally in the month of September, the shore of the Ottawa 

 for about two miles from the mouth of the creek upwards, is 

 strewn with nodules of all manner of curious shapes washed from 

 the base of the steep bank of clay which rises from high water 

 mark. 



In looking over the collection of nodules from this locality in 

 the Museum of the Geological Survey, I found two specimens oi 

 Limncea stagnalis, one of our commonest living species. Both 

 had been partially filled with clay, now a hard stone, while they 

 still retained their original shape. With the exception of the 

 splendid Limncea meyasoma, which inhabits the Ottawa valley, 

 this is the largest species in Canada. It was called L. jugularis 

 by Say, but is identical with the European L. stagnalis. One 

 meets with these shells in almost every warm marsh or pond on 

 the south side of the Ottawa, and it is interesting to know that 

 their progenitors lived in this country while the Leda clay was 

 being deposited and a deep sea covered their present abode. 



* Canadian Naturalist, vol. iv. p. 36, vol. 11, p. 422. 



