And here is part of the description
The white clawed crayfish have a single pair of post-orbital (behind the eyes) ridges unlike the signal crayfish that has two pairs. The body of white-clawed crayfish is smooth, generally brown to olive in colour with a pitted appearance. Signal crayfish also have a smooth body but the colour is often more reddish-brown. Claws of signal crayfish are smooth and red on the underside with a white-turquoise patch on top of the junction of claw. White-clawed crayfish have rough top sides of their claws with dirty-white to pink colour on the underneath
Mur