Among the Titanotheriidae Palaeosyops[161] has very brachydont teeth whose crowns have been described as buno-selenodont, the inner pair of columns being bunodont, the outer, selenodont. Similar grinding teeth occur in Chalicotherium. Some of the Titanotheriidae have the regular mammalian series of forty-four teeth.
Subungulata.
Toxodontia. Nesodon has the regular dental formula; its grinding teeth are rooted and the upper ones resemble those of Rhinoceros. The second upper and third lower incisors form ever-growing tusks. There is a marked difference between the deciduous and permanent dentition. Astrapotherium likewise has large rooted cheek teeth of a rhinocerotic type, and each jaw bears a pair of permanently growing tusks, those of the lower jaw being the canines. The dental formula is
i 1/3 c 0/1 pm 2/1 m 3/3, total 28.
In Toxodon the upper incisors and molars are large and curved and all the teeth have persistent pulps. In Typotherium there are no tusks, but the upper incisors are chisel-like, recalling those of Rodents.
The Condylarthra have brachydont, generally bunodont teeth, with the premolars simpler than the molars. They generally have the regular dental formula.
Hyracoidea. The dental formula of Procavia is usually given as i ½ c 0/0 pm 4/4 m 3/3, total 34; in young individuals however there occur a second pair of upper incisors which early fall out. The upper incisors resemble those of Rodents in being long and curved and growing from persistent pulps. They are however triangular in transverse section, not rectangular, having two antero-lateral faces covered with enamel and a posterior face without enamel. Their terminations are pointed, not chisel-shaped as in Rodents. The lower incisors (fig. 83, i 1) are pectinate or partially divided by vertical fissures, and the grinding teeth are of the rhinocerotic type.
Fig. 83. Skull of Procavia (Dendrohyrax) dorsalis × 2/3. (Camb. Mus.)
| 1. nasal. | 5. jugal. |
| 2. parietal. | 6. lachrymal foramen. |
| 3. external auditory meatus. | i 1. first incisor. |
| 4. paroccipital process of the | |
| exoccipital. |