All the foregoing are natives of Madagascar. It has been suggested however, that two remarkable West Indian insectivores, namely Solendon cubanus of Cuba (fig. 11) and S. paradoxus of Hayti, should be regarded as representing merely a subfamily Solenodon. of Centetidae. It is true that the main features distinguishing these strange creatures from the Malagasy representatives of that family are the constriction of the skull behind the orbits, the descent of the testes into the perineum, and the post-inguinal position of the teats, and that none of these are of very great importance. But the geographical positions of the two groups are so widely sundered that it seems preferable to await further evidence before definitely assigning the two to a single family; and the family Solenodontidae may accordingly be retained for the West Indian animals. Solenodons, which look like huge long-nosed, parti-coloured rats, have the tibia and fibula separate, and the same dental formula as Microgale. Each of the two species (which differ in colour and the quality of the fur) has a long cylindrical snout, an elongated naked tall, feet formed for running, and the body clothed with long, coarse fur. The position of the teats on the buttocks is unique among Insectivora. The first upper incisors are much enlarged, and like the other incisors, canines and premolars, closely resemble the corresponding teeth of Myogale; the second lower incisors are much larger than the upper ones, and hollowed out on the inner side.
| Fig. 12.—A Golden Mole (Chrysochloris obtusirostris) reduced. |
The last family, Chrysochloridae, is represented by the golden moles of South and East Africa, which differ from the Centetidae and Solenodontidae by the development of a bulla to the tympanic, and the presence of a zygomatic arch to the Golden Mole. skull; the tibia and fibula being separate, and the symphysis of the pelvis formed merely by ligament. The skull is not constricted across the orbits. The teats, which are placed both on the breast and in the groin, are situated in shallow depressions. The ears are buried in the fur, and the eyes concealed beneath the skin; the feet are four-toed and provided with powerful claws for burrowing in the fashion of the mole, but it is interesting to note that the skeleton is modified for the same purpose in a manner quite different from that obtaining in the latter animal. These animals derive their name from the metallic iridescence of the fur of most of the species. In the more typical species the dental formula is the same as in Microgale, that is to say, there are 40 teeth. In other species, which it has been proposed to separate as Amblysomus, there are, however, only 36 teeth, owing to the absence of the last pair of molars. The group is evidently nearly related to the Centetidae—most nearly perhaps to the Oryzorictinae.
Fossil Insectivora.
Some years ago Dr F. Ameghino, of Buenos Aires, described from the Tertiary formation of Santa Cruz, in Patagonia, the remains of an insectivore under the name of Necrolestes. The occurrence of a member of the Insectivora in these beds is remarkable, since this group is represented at the present day in South America only by a shrew or two which have wandered from the north. Dr Ameghino expressed his belief that the extinct Patagonian insectivore was nearly related to the golden moles, and although this opinion appears to have been withdrawn, Professor W. B. Scott states that he is convinced of the close affinity existing between Necrolestes and Chrysochloris. Although this view may not be accepted, it must be remembered that it represents the opinion of a palaeontologist who has had better opportunities than most of his fellow-workers of forming a trustworthy judgment. So convinced is Dr Scott of the closeness of the relationship between Necrolestes and the golden moles that he regards it as rendering probable the former existence of a direct land-connexion between Africa and South America. There is no reason, he says, to suppose that the track of migration could have been by way of Europe and North America, for no trace of the group has been found anywhere north of the equator. This supposed connexion between Africa and South America in Tertiary times has often been suggested, and is supported by many independent lines of evidence; and the presumed affinity between the two mammals here referred to adds to the weight of such evidence.
The discovery in the Oligocene Tertiary deposits of Dakota of the remains of a species of hedgehog is a fact of great interest, for the hedgehog-tribe (Erinaceidae) is at the present day an exclusively Old World group. The discovery of the fossil American species, which has been made the type of a new genus under the name of Protherix, serves to strengthen the view that the northern countries of the Western and Eastern hemispheres form a single zoological region; and that formerly there was comparatively free communication between them in the neighbourhood of Bering Sea, under climatic conditions which permitted of temperate forms passing from one continent to the other. As might have been expected, remains of hedgehog-like mammals have been obtained in the Tertiary deposits of Europe. Among these, Palaeoerinaceus, from the Upper Oligocene of France, seems scarcely separable from the existing genus. Necrogymnurus (Neurogymnurus) from the Lower Oligocene, of the same country, appears to be allied to Hylomys, which is itself the most generalised of the family, so that the extinct genus, of which Caluxotherium is a synonym, may represent the ancestral type of the Erinaceidae. The genus Galerix, or Lanthanotherium, of the Oligocene, which has the typical series of 44 teeth, a bony ring round the orbit, and conjoint tibia and fibula, has been regarded as representing the Tupaiidae and Macroscelididae, but is more probably referable to the Erinaceidae, being apparently akin to Gymnura. The moles are represented in the French Oligocene by Amphidozotherium and in the Miocene by Talpa, while in the North American early Tertiary we have the primitive Talpavus. Shrews are also known from the Lower Oligocene upwards both in the eastern and western hemispheres. Of the Lower Eocene Adapisorex, with the typical 22 lower teeth, Adapisoriculus and Orthaspidotherium, all from France, the affinities are quite uncertain. The American Oligocene Leptictis, with i. 2, c. 1, p. 4, m. 3 in the upper jaw, and Ictops, with i. 3⁄2, c. 1⁄1, p. 4⁄4, m. 3⁄3, may be insectivorous mammals, with affinities to the creodont Carnivora. It is, indeed, probable that not only is there a relationship between the Creodonta and the Insectivora, but also one between the latter and the Marsupialia, so that the marked similarity between the cheek-teeth of the insectivorous Chrysochloris and the Marsupial Notoryctes may be due to genetic relationship. That the bats and the flying-lemur are descendants of the Insectivora cannot be doubted.
Bibliography.—G. E. Dobson, “Monograph of the Insectivora” (London, 1883-1890); W. Leche, “Zur Morphologie des Zahnsystems der Insectivoren,” Anatom. Anzeiger (xiii. 1 and 514, 1897); C. J. Forsyth-Major, “Diagnoses of New Mammals from Madagascar.” Ann. Mag. Nat. Hist. ser. 6. vol. xviii. pp. 318 and 461 (1896): A. A. Mearns, “Descriptions of New Mammals from the Philippine Islands,” Proc. U.S. Museum (xxviii. 425, 1905).
(R. L.*)
INSECTIVOROUS PLANTS. Insectivorous or, as they are sometimes more correctly termed, carnivorous plants are, like the parasites, the climbers, or the succulents, a physiological assemblage belonging to a number of distinct natural orders. They agree in the extraordinary habit of adding to the supplies of nitrogenous material afforded them in common with other plants by the soil and atmosphere, by the capture and consumption of insects and other small animals. The curious and varied mechanical arrangements by which these supplies of animal food are obtained and utilized are described under the headings of the more important plants.