This study presents the results of morphometric analysis of a total of 473 skulls ascribed to adult animals were sufficiently complete to allow the measurement of their foramen magnum; and for 472 of them the foramen magnum index could be calculated. The dorsal notch was only seen in the group of mesocephalic dogs where about 17% of all skulls exhibited this feature. The average length of the dorsal notch was found to be 2.59 mm. Not a single skull in the dolichocephalic dog group showed any sign of a dorsal notch. The results of this study show that the dorsal notch in the foramen magnum widely seen dogs of the Middle Ages, and point to a morphological variation.