Someone told me that it could be a Snuff bottle ?
Interesting find! I definitely think it's a western design, not a Chinese one. I'm wondering if maybe it was for some sort of toiletry, I could see that sitting on someone's bathroom cabinet.
Are you digging these days? I'm in Montreal as well, haven't done any digging in ages but I did notice last fall that there was excavation going on at that dump down by the Victoria Bridge, probably lots to find down there if the construction crews are co-operative.