projects 12 millimeters beyond the third molar, while the average for the males is 8.6 millimeters. Respecting the series of lower jaws, I quote from my paper read in 1902: "The third molar is generally situated well in front of the ascending ramus of the lower jaw, when the jaw is so held as to bring the anterior margins of the rami in a line with the eye. With the jaAV held in this position, the entire crown of the third molar can be seen in 13 out of a total of 18 cases."
The crowns of the teeth in the Mauer specimen are worn enough to show the dentine, proof that the individual had reached the adult stage. All the molars, except the third left, have five cusps. The tendency in recent man is toward a four-cusp type for the third molar, if indeed there be a third molar. The breaking away of the crowns of four teeth on the left side tended to facilitate the study of the pulp cavities and the walls. This study reveals the fact that the dentition of Homo heidelhergensis represents a youthful stage in the dentition of the modern European. That is to say, in the ontogeny of the latter, a stage representing adult dental characters when the race was young is now reached at the age of from 9 to 14 years. This is not an anthropoid character, but a primitive human character—another reason for leaving the anthropoids to one side in our search for the ancestral form and the origin of genus Homo.
A study of the corpus and ramus mandibulæ reveals at once a number of points of divergence from the modern European. The body is massive, and relatively long in proportion to the bicondylar breadth, its greatest height being in the region of the first and second molars. The basis mandibulæ, if applied to a plane, touches only on either side of the symphysis and near the angulus, forming three gentle arches—one median and short, called by Klaatsch incisura sub-mentalis; and two lateral and long, to which might be given the name incisura basilaris. The latter is seen to good advantage also in the chimpanzee.
The ramus is characterized by unusual breadth, 60 millimeters as opposed to an average of 37 for recent examples. The angle formed by lines tangent to the basis and the posterior border of the ramus is 107°—smaller than the average. The processus coronoideus is exceedingly blunt, and the incisura mandibular correspondingly shallow. The condyloid process is noteworthy on account of the extent of articular surface, due to an increased antero-posterior diameter (13 and 16 millimeters), since the transverse diameter is relatively short. The neck constriction is very slight, approaching in this respect the anthropoid forms.
The first fossil lower jaw to attract world-wide attention on account of its primitive characters and association with remains of
