Even without seeing the rump, you can tell it's a Pem. The ears are more pointed than a Cardi's. The most obvious thing though, is the color. While it's POSSIBLE to find red-headed tricolor Cardigans (that color that the dog in the picture is- it's also called 'hound tri' in some breeds), nearly all tricolor Cardigan Corgis are black-headed tris (BHT does occur in Pems, but it's not very common).
here's a photo of a black-headed tricolor (Cardigan) Corgi, my boy Indy.
