Bilateral Symmetry-is when an organism can be divided into right and left halves, identical but mirror images, by a single vertical plane. The external form of humans displays this symmetry, though...
Externally, dogs (and also humans) have bilateral symmetry. Internally there are some organs that are on left or right but not both, so there is not internal symmetry.
As with most mammals (if not all), dolphins are radial symmetric. Animals such as jellyfish are bilateral symmetric (meaning they have a symmetry around an axis).