Family VI.—PHYLLOSTOMIDÆ.
Sub-family 1.—Lobostominæ.—Nostrils in front of muzzle; chin with erect cutaneous ridges. Genera.—Chilonycteris, Pteronetus, Mormops.
Sub-family 2.—Phyllostominæ.—Nostrils on upper surface of muzzle; chin with warts. Group 1.—Vampyri.—Molars with W-shaped cusps; four upper incisors; muzzle long; tongue moderate. Genera.—Macrotus, Lonchorhina, Macrophyllum, Vampyrus, Schizostoma, Lophostoma, Trachyops, Phyllostoma, Carollia, Rhinophylla. Group 2.—Glossophagæ.—Like the Vampyri, but tongue very long, and lower lip divided by a deep groove. Genera.—Glossophaga, Monophyllus, Ischnoglossa, Phyllonycteris, Lonchoglossa, Glossonycteris. Group 3.—Stenodermata.—Muzzle short; molars with a cutting outer edge; four upper incisors. Genera.—Stenoderma, Artibeus, Phyllops, Vampyrops, Pygoderma, Ametrida, Chiroderma, Sturnira, Brachyphylla, Centurio. Group 4.—Desmodontes.—No true molars; two upper incisors. Genera.—Desmodus, Diphylla.
We have already remarked that of these families the Vespertilionidæ may be regarded as the types of the whole order; they realise all the notions that we form in our minds when we speak of “a Bat,” and this with the greatest simplicity, or with the smallest amount of complication from subordinate characters. Next to them in this respect come some of the Emballonuridæ. The other families group themselves round these, or the whole of the other Microchiroptera may be said to surround the Vespertilionidæ. Mr. Dobson, accepting the notion of the origin of organic forms by a process of evolution, assumes an unknown group of ancestral forms (Palæochiroptera) from which in the first place the Vespertilionidæ and Emballonuridæ diverge, forming the roots of his two “alliances.” From the Emballonuridæ proceed the Phyllostomidæ, and from the Vespertilionidæ the Nycteridæ and Rhinolophidæ. From this point of view these Bats may be regarded as allied to the Insectivora through some unknown common ancestors; but what these may have been, or by what stages the Bat-type originated from the ordinary quadruped, it is very difficult to imagine. The facts of geographical distribution go far, however, to confirm the view that the Vespertilionidæ and Emballonuridæ are the central and oldest types of Bats; their distribution is world-wide, and even some nearly allied forms are found in very distant parts of the world. The other families are more restricted in their range, the Nycteridæ and Rhinolophidæ being confined to the Eastern, and the Phyllostomidæ to the Western hemisphere, and chiefly to the warmer zones, whereas the Vespertilionidæ extend much further to the north.
The Pteropidæ, or Frugivorous Bats, however, cannot well be brought into this scheme of descent. They stand completely isolated from the rest of the order, and their peculiar distribution would almost seem to indicate that their origin and relationships were distinct from those of the other Bats. Their range, which sweeps round the shores of the Indian Ocean from the Cape of Good Hope to Australia, and extends, perhaps somewhat exceptionally, into the islands of the Pacific, although it cannot be said to coincide with that of the Lemuroids, being so much wider, at least includes the whole of the localities in which the latter are met with; and if the Lemuroids are really, as seems probable, segregated descendants of a great fauna which inhabited the supposed sunken continent of “Lemuria,” the same origin may fairly be ascribed to the Pteropidæ, and their wider distribution may be accounted for by their much greater power of locomotion. In connection with this it is interesting to note the strong Lemurian resemblances presented by many of the Pteropidæ; and further, the sort of common point of junction between the Lemuroids, the Pteropids, and the Insectivora, furnished by that curious animal the Galeopithecus, or Flying Lemur, which is also still an inhabitant of a region haunted by Lemuroids and Pteropine Bats. The Pteropidæ thus seem to stand quite apart from the other Bats. From a genealogical point of view, which indeed is that which we always take of the relationships of animals, whether we believe in the doctrine of descent or not, we may ask whether the two sub-orders of Bats have not been realised in their present form through two quite different series of modifications.
The appeal to fossil evidence, which in some cases leads to satisfactory results, gives us no clue to the origin of the different groups of Bats. Of the Pteropidæ no fossil remains are known. Of the other families the most ancient remains are, as might be expected, those of the Vespertilionidæ, several species of which have been found in Miocene beds at Mayence and in the south of France, and even in the Eocene gypsum deposits of the Paris basin. Other bones identical with those of species now living in the same localities have been detected in bone-caves in various parts of Europe. Bones of a Rhinolophus have occurred in the cavern of “Kent’s Hole,” near Torquay; and the celebrated bone-caves Brazil have furnished numerous remains of Bats, all of which, however, are referable to the peculiarly South American family Phyllostomidæ. Thus, so far as we are acquainted with them, the fossil remains of Bats, even the most ancient, indicate only forms more or less nearly related to those still existing in the same localities, and furnish us with no means even of speculating upon the course of events by which, so to speak, the type of the Chiroptera was evolved.
W. S. DALLAS.
LOW’S PTILOCERQUE.