Head planes are not the same. Rounded Skull. Incorrect for a working terrier. This weakness in the head makes the dog much more venerable to being grabbed by the quarry while underground. You can see the back skull slopes away from the eyes, providing less protection from dirt and attack. This bitch's muzzle is a bit snipey and does not show the strength needed to survive the attacks of whatever she may encounter underground. The end of the muzzle is slanted downward. She is lacking the strength/finish of the proper underjaw.
Parallel head planes. Flat Skull. This is the correct head type for the working terrier. This dog has adequate protection above the eyes. Notice also his strong powerful jaws enabling him to take much more punishment underground. This dog could also better hold the quarry until it was dug to, if need be. Notice the nice finish to the underjaw, which shows strength. The end of the muzzle is blunt.
The flat back skull also allows for proper eye placement on the terrier's head.
Every detail in the conformation of the breed should be functional for the purpose of earthwork. The Russell Terrier is the ultimate working earth terrier. The terriermen of England bred for functional attributes to assist the breed at work and have since the 1800's. Never in the history of the breed has any standard been written describing the skull as being slightly rounded. The head should be flat with no roundness to the skull what so ever. If you tighten up your hand into a fist and place your fist in the mouth of a dog, they have a very difficult time grabbing on to the flat surface. However, if you give them a round object they can easily grab hold or pick it up due to the shape. Any roundness to the skull would give the Russells a clear disadvantage at work not allowing for protection of the head. They need the flat skull that extends to the forehead which provides a shelf for additional protection over the eyes. Any roundness about the eyes would take away that protection. The Russells meet their quarry underground with their heads taking all of the punishment. The jaw should be strong and punishing. The muzzle should be a blunt wedge shape with sufficient under jaw. A triangle shaped head would not only give the terriers less room for sufficient sized teeth but would add additional length to the muzzle that would again be an advantage for the quarry they meet. The triangle shaped head would place the eyes to the side of the head restricting centered vision and when the terriers work underground would not give enough protection to the eyes. Centered eye placement gives the terriers protection from the side of the jaw and the shelf above the eye. The Russell Terrier is designed for work. The breed could be described as a head breed in the fact it must have the correct head to do the work it was intended to do.
