According to the American Kennel Club…
Head: Small in proportion to body and proudly carried., giving an impression of quality. Masculine in dogs but free from coarseness.
Skull: Slightly domed, moderate width and length.
Neck: Moderately short, strong and well set on.
Ears: Medium size, pendant, well feathered in the adult and set fairly high. They may have a slight lift from the skull but should not fly.
Eyes: Dark brown in color, oval in shape, bright and expressive, of medium size set fairly well apart but forward looking, giving an apelike expression. Eye rims black.
Muzzle: Medium length, blunt with cushioning. Free from wrinkle.
Teeth: Evenly placed and the lower jaw wide between the canine tusks. Full dentition desired. A level mouth is permissible, providing there is sufficient depth and width of chin to preserve the blunt appearance of the muzzle.
Forequarters: Shoulders are well placed. The bones of the forelegs are slightly bowed but firm at the shoulder. Moderate bone.
Tail: Set high, richly plumed and carried in a gay curl over the back when moving.
Hindquarters: Well made and strong. Stifle well developed, showing moderate angulation. Hocks well let down and straight when viewed from behind.
Coat: Double coat, silky in texture,smooth on face and front of legs, of moderate lenght on body, but lying rather flat. Ears and back of forelegs are nicely feathered, tail and buttocks well furnished with longer hair. Neck covered with a mane or “shawl” of longer hair, which is more pronounced in dogs than bitches. Feathering between toes often extending beyond the feet.
Color: All colors and mixtures of colors are allowed. Feet – white markins are allowed.
Weight: 9-15 pounds (4-6 kgs) being ideal.
Size: About 10 inches (25 cm).