After about 25 rounds of different people guessing at what on Earth Barnacle is, I've decided to lay my bet on the table.
I'm laying odds that Barnacle is a Beagle-Lab mix.
My reasoning? Setting aside the fact that I know next to nothing about dogs, I had a yellow lab and a beagle growing up. I vaguely remember them both as puppies, and Rosie (the yellow lab) was bulkier than Barnacle at 9 weeks. Rosie was wider and more gangly as well. I've also looked up weights for lab puppies, and for 9 weeks he should be almost 20 pounds, and he's only 10.5 pounds. Barnacle also has giant ears, much bigger than a labrador's ears, however not quite as big as a beagle. His paws aren't huge, but they're not tiny either, and he's clumsy as hell. I'm not sure if that's a lab or beagle thing, but it's funny.
I think he's a mix of the two, I know for sure he's not all lab. I'm also pressing the idea because I think it would be weird to end up with a dog who's a mixture of my first two dogs.