The Parson Russell Terrier is named for the Reverend John Russell, a nineteenth-century hunting parson in Devon, England, who wanted a mostly white terrier with legs long enough to keep up with foxhounds. Today's Parson is the longer-legged, square-built relative of the Jack Russell, about 13 to 14 inches tall and usually 13 to 17 pounds, with a smooth or broken coat that's mostly white with black or tan markings.
Many Parsons are bold, friendly and affectionate at home, with energy that seems to have no off switch. They dig, chase and bark when bored, and some are scrappy with other dogs. In SF, that means a dog who'll be wound up by busy sidewalks and crowded dog play areas, so training and a sturdy leash matter. Parsons vary, and the best matches are active, patient adopters who enjoy teaching tricks.