This is the view of a 20-year-old horse’s top teeth with his mouth open. The Galvayne’s groove extends the entire labial surface length of the upper corner incisor of the 20-year-old horse....
This illustration shows that in a 15-year-old horse's teeth, the Galvayne's groove extends about halfway down the labial surface of the corner incisor.
This illustration of an 8-year-old horse's teeth from the side (lateral view) shows the upper and lower incisors ar at a more oblique angle than in younger horses.