Puppy

We've decided to get another puppy -- a companion for Costa. The problem is, we don't know what we want to get. We went looking around yesterday and while there are some adorable puppies at the Humane Society, most were black lab mixes -- which grow up to be too big for our liking. I'd LOVE to get a golden retriever, but they too are too big. On the other side of things, we don't want one of those little dogs either. Something medium, like Costa. Any suggestions?