1. condyle.pm 1, pm 4. first and fourth
2. coronoid process.premolars.
i 3. third incisor.m. molar.
c. canine.

In the Pinnipedia the dentition differs considerably from that of the Carnivora vera. The milk dentition is always vestigial, and the teeth are frequently absorbed before birth. There are four premolars and one molar, forming an uniform series of cheek teeth, all of which except in the Walrus have compressed and pointed, never flattened, crowns. There is no special carnassial tooth, and the incisors are always fewer than 3/3. In Otaria the dentition is

i 3/2 c 1/1 pm 4/4 m 1 or 2/1, total 34 or 36.

In the Walrus the upper canines form immense tusks. The other teeth are all small and one-rooted, and the molars have flat crowns. In the true seals the dentition is strikingly piscivorous, the cheek teeth often having accessory cusps (fig. 86).

The Insectivora are diphyodont and heterodont, having well-developed rooted teeth. The canines are usually weak, the incisors pointed, and those of the two jaws often meet like a pair of forceps. The crowns of the molars are characteristically studded with short cusps. Some genera, such as Gymnura and the mole, Talpa, have the regular mammalian dentition. In the hedgehog, Erinaceus, the dentition is

i 3/2 c 1/1 pm 3/2 m 3/3, total 36.

In the genus Sorex (Shrews) the teeth differ in the following two marked respects from those of most other Monodelphia, (1) they are monophyodont, (2) the lower incisors sometimes become fused to the jaws. Most Insectivora have square molar teeth, but in Potamogale, Chrysochloris, Solenodon and the Centetidae the molar teeth are triangular in section. Four molars occur in Centetes.

In the aberrant genus Galeopithecus the dentition is i 2/3 c 1/1 pm 2/2 m 3/3, total 34. The upper incisors are placed at some distance from the anterior end of the jaw, and the outer upper incisors and canines of both jaws have two roots,—a very unusual character. The lower incisors are deeply grooved or pectinated in the same way as are the lower incisors of Procavia. The upper incisors and canines of both jaws bear many cusps, and are very similar in appearance to the cheek teeth of some Seals.

The dentition of the Chiroptera is diphyodont and heterodont, and the dental formula never exceeds