More than twenty teeth in the temporary set, or thirty-two in the permanent set, is hence an atavistic abnormality. From the maxillary and dental standpoint man reached his highest development when well-developed jaws held twenty temporary and thirty-two permanent teeth. Decrease in the numbers of teeth meant, from the dental standpoint, degeneracy, albeit it might mark advance in man's evolution as a complete being. In the New Mexican Lower Eocene occur monkeys like the lemurarius and limnotherium, each the type of a distinct family. The lemurarius, most nearly allied to the lemurs, is the most generalised monkey yet found. It had forty-four teeth in continuous series, above and below. The limnotherium, while related to the lemurs, had some affinities with the American marmosets. These solved the problem of the origin of the extra teeth (known as supernumeraries) that sometimes occur in man, and demonstrated that man, during his evolution from the lowest monkey, lost twelve teeth. These supernumerary teeth assume two forms; either they resemble the adjoining teeth or are cone-shaped. While they are rarely exactly counterparts, every tooth can be duplicated, as the following illustrations show. Fig. 52 illustrates fairly well-formed duplicate central incisors, the normal incisors being outside the dental arch. They are crowded laterally by the large roots of the supernumerary incisors. [Illustration: FIG. 52.] [Illustration: FIG. 53.] [Illustration: FIG. 54.] Fig. 53 shows an extra right lateral in a temporary set in the upper jaw. Fig. 54 an extra right lateral in the permanent set. Fig. 55 illustrates normally developed supernumerary cuspids which are all grouped together upon the right side, the bicuspid being also duplicated on each side; indeed, all but the molars are duplicate. Fig. 56 shows supernumerary third molars, easily demarcated from the normal molars. The teeth which fail to approximate their normal neighbours assume the cone shape of the primitive tooth. [Illustration: FIG. 55.] [Illustration: FIG. 56.] The fact that the cone-shaped tooth, as a rule perfect in construction, is found everywhere in the jaw, but especially in the anterior and posterior part of the mouth, is of much value in outlining tooth and jaw evolution, especially in the degeneracy phase. The upper jaw, being an integral part of the skull and fixed, is, of necessity, influenced by brain and skull growth; hence degeneracy is more detectable in it than in the lower. [Illustration: FIG. 57.] [Illustration: FIG. 58.] [Illustration: FIG. 59.] [Illustration: FIG. 60.] [Illustration: FIG. 61.]