Curiously enough the European hedgehog (E. europaeus) is the most aberrant species, differing from all the rest in the peculiarly-shaped and single-rooted third upper incisor and first premolar (fig. 7, A), and in its very coarse harsh fur. The dentition of the long-eared Indian E. grayi (fig. 7, B) may, on the other hand, be considered characteristic of all the other species, the only important differences being found in the variable size and position of the second upper premolar, which is very small, external and deciduous in the Indian E. micropus and E. pictus. The former species, limited to South India, is further distinguished by the absence of the jugal bone. Of African species, E. diadematus, with long frontal spines, is probably the commonest, and E. albiventris has been made the type of a separate genus on account of the total absence of the first front-toe. See [Hedgehog].
The members of the second subfamily, Gymnurinae, are more or less rat-like animals, confined to the Malay countries, and easily distinguished from the hedgehogs by the absence of spines among the fur and the well-developed tail. They also lack Rat-shrew. vacuities in the palate, and have a long and narrow pelvis. The typical representative of the family is the greater rat-shrew, or greater gymnura (Gymnura rafflesi) a creature which may be compared to a giant shrew, and whose colour is partly black and partly white, although a uniformly pale-coloured race. (G. r. alba) inhabits Borneo. In common with the next genus, it has the full series of 44 teeth; and its range extends from Tenasserim and the Malay Peninsula to Sumatra and Borneo, the island individuals being stated to be considerably larger than those from the mainland. In this species the length of the tail is about three-fourths that of the head and body; but in the lesser rat-shrew (Hylomys suillus), ranging from Burma and the Malay Peninsula to Java and Sumatra, the former dimension is only about one-sixth of the latter. In the Philippines the group is represented by Podogymnura truei, distinguished from the other genera by the great elongation of the hind-foot, the tail being likewise long. There are only three pairs of premolars in each jaw.
| Fig. 7.—Fore-part of Skulls of Common Hedgehog (Erinaceus europaeus), A, and Gray’s Hedgehog (E. grayi), B, much enlarged. |
| Fig. 8.—The Insectivorous Otter (Potagmogale velox). |
In the remaining families of the Insectivora the tibia and fibula may be either separated or united at the lower end; there is no descent of the testes, except in Solenodon; a short symphysis is formed by the junction of the pubic epiphyses; Insectivorous Otter. and the upper molars are generally small, and triangular, with three cusps arranged in a V. The first family, Potamogalidae, is represented by the otter-like Potamogale velox of the rivers of West Africa (fig. 8), distinguished from all other members of the order by the absence of clavicles. The tibia and fibula are united interiorly, the skull has a ring-like tympanic, no zygomatic arch, and the upper molars are of the tuberculo-sectorial type, with broader crowns than in the following families. The dental formula is i. 3⁄3, c. 1⁄1, p. 3⁄3, m. 3⁄3, total 40. This animal inhabits the banks of streams in west equatorial Africa, and its whole structure indicates an aquatic life. It is nearly 2 ft. in length, the tail measuring about half. The long cylindrical body is continued uninterruptedly into the thick laterally compressed tail, the legs are very short, and the toes are not webbed, progression through the water depending wholly on the action of the powerful tail, while the limbs are folded inwards and backwards. The muzzle is broad and flat, and the nostrils are protected by valves. The fur is dark brown above, the extremities of the hairs on the back being of a metallic violet hue by reflected light, beneath whitish.
| Fig. 9.—Skull of the Tenrec (Centeles ecaudatus), somewhat reduced. |
In the remaining groups the upper molars form narrow V’s of the true tritubercular type. The family, Centetidae, represented by the tenrec and a number of allied animals from Madagascar, is specially characterized by the ring-like tympanic, and Tenrec. the absence of a zygomatic arch and of any constriction of the skull behind the orbits, and the presence of teats on the breast as well as the abdomen. In the more typical members of the family the tibia and fibula are separate, and, as in hedgehogs, spines are mingled with the fur. The true or great tenrec (Centetes ecaudatus), alone representing the typical genus, has the dental formula i. (3 or 2)/3, c. 1⁄1, p. 3⁄3, m. (3 or 4)/(3 or 4), total 38, 40, 42 or 44. The fourth lower molar, when developed, does not appear till late in life. Of the long and sharp canines, the tips of the lower pair are received into pits in the upper jaw (fig. 9). The creature grows to a length of aoout a foot. The young have strong white spines arranged in longitudinal lines along the back, but these are lost in the adult which has only a crest of long rigid hairs on the nape of the neck. The lesser tenrecs, Hemicentetes semispinosus and H. nigriceps, are distinguished by the persistence of the third upper incisor and the form of the skull. The two species are much smaller than the great tenrec, and spines are retained in the adult on the body. The hedgehog-tenrec, Ericulus setosus, has the whole upper surface, and even the short tail, densely covered with close-set spines. The facial bones are much shorter than in the preceding genera, and the first upper incisors are elongated; while there are only two pairs of incisors in each jaw. Judging from the slight development of the cutaneous muscles compared with those of the hedgehog, it would seem that these creatures cannot roll themselves completely into balls in hedgehog-fashion. A second species of this genus, Ericulus (Echinops) telfairi, has two, in place of three, pairs of molars, thus reducing the total number of teeth to 32. Moreover, the zygomatic arches of the skull are reduced to mere threads. Here should perhaps be placed Geogale aurita, a small long-tailed Malagasy insectivore, with 34 teeth, and no spines; the tibia and fibula being separate. It has been classed in the Potamogalidae, but from its habitat such a reference is improbable. The absence of spines may entitle it to separation from the Centetinae, so that it should perhaps be regarded as representing a subfamily, Geogalinae, by itself.
| Fig. 10.—Skull of the Lesser Tenrec (Hemicentetes spinosus). |
The absence of spines coupled with the union of the tibia and fibula form the leading characteristics of the subfamily Oryzorictinae, typified by the rice-tenrecs Oryzorictes, of which there are several species. These creatures, which excavate burrows in the rice-fields of Madagascar, are somewhat mole-like in appearance, but have tails of considerable length. In the typical O. hova the fore-feet are five-toed, but in O. tetradactylus the number of front digits is reduced to four. The long-tailed tenrecs (Microgale) are represented by fully half-a-dozen species with tails of great length; that appendage in the typical M. longicaudata being more than double the length of the head and body, and containing no fewer than forty-seven vertebrae. The teeth are generally similar to those of Centetes, but are not spaced in front; their number being i. 3⁄3, c. 1⁄1, p. 3⁄3, m., 3⁄3, total 40, or the same as in Oryzorictes. Finally, Limnogale mergulus, a creature about the size of a black rat, has webbed toes and a laterally compressed tail, evidently adapted for swimming. See [Tenrec].
| Fig. 11.—Solenodon cubanus. |