3 scribed by Dr. Gunther in his catalogue. These forms extend from Java and Borneo on the one hand, to Aleppo on the other. Nevertheless a new species (M. cryptacanthus) has been described by the same author, which is an inhabitant of the Camaroon country of Western Africa. He observes: The occurrence of Indian forms on the West Coast of Africa, such as Periophthalmus, Psettus, Mastacembelus, is of the highest interest, and an almost new fact in our knowledge of the geographical distribution of fishes." 4 Ophiocephalus, again, is a truly Indian genus, there being no less than twenty-five species, all from the fresh waters of the East Indies. Yet Dr. Günther informs me that there is a species in the Upper Nile and in West A frica. The acanthopterygian family (Labyrinthici) contains. nine fresh-water genera, and these are distributed between the East Indies and South and Central Africa. The Carp fishes (Cypronoids) are found in India, Africa, and Madagascar, but there are none in South America. Thus existing fresh-water fishes point to an immediate connection between Africa and India, harmonizing with what we learn from Miocene mammalian remains. On the other hand, the Characinidæ (a family of the physostomous fishes) are found in Africa and South America, and not in India, and even its component groups are so distributed,-namely, the Tetragonopterina and the Hydrocyonina." 5 Again, we have similar phenomena in that almost exclusively fresh-water group the Siluroids. 2 See his Catalogue of Acanthopterygian Fishes in the British Museum, vol. iii., p. 540. 3 Proc. Zool. Soc., 1867, p. 102, and Ann. Mag. of Nat. Hist. vol. xx., p. 110. 4 See Catalogue, vol. iii., p. 469. Ibid., vol. v., p. 311. 6 Ibid., p. 345. 7 Thus the genera Clarias Heterobranchus are found both in Africa and the East Indies. Plotosus is found in Africa, India, and Australia, and the species P. anguillaris' has been brought from both China and Moreton Bay. Here, therefore, we have the same species in two distinct geographical regions. It is, however, a coast fish, which, though entering rivers, yet lives in the sea. Eutropius 10 is an African genus, but E. obtusirostris comes from India. On the other hand, Amiurus is a North American form; but one species, A. Cantonensis," comes from China. The genus Galaxias 12 has at least one species common to New Zealand and South America, and one common to South America and Tasmania. In this genus we thus have an absolutely and completely fresh-water form of the very same species distributed between different and distinct geographical regions. 13 Of the lower fishes, a lamprey, Mordacia mordax,13 is common to South Australia and Chili; while another form of the same family, namely, Geotria Chilensis," is found not only in South America and Australia, but in New Zealand also. These fishes, however, probably pass part of their lives in the sea. We thus certainly have several species which are common to the fresh waters of distant continents, although it cannot be certainly affirmed that they are exclusively and entirely fresh-water fishes throughout all their lives except in the case of Galaxias. Existing forms point to a close union between South America and Africa on the one hand, and between South America, Australia, Tasmania, and New Zealand, on the other; but these unions were not synchronous any more See Catalogue, vol. iii., p. 13. 10 Ibid., p. 52. * Ibid., p. 21. 11 Ibid., p. 100. 14 Ibid., p. 509. than the unions indicated between India and Australia, China and Australia, China and North America, and India and Africa. Pleurodont lizards are such as have the teeth attached by their sides to the inner surface of the jaw, in contradistinction to acrodont lizards, which have the bases of their teeth anchylosed to the summit of the margin of the jaw. INNER SIDE of LoweR JAW OF PLEURODONT LIZARD. (Showing the teeth attached to the inner surface of its side.) Now pleurodont iguanian lizards abound in the South American region; but nowhere else, and are not as yet known to inhabit any part of the present Continent of Africa. Yet pleurodont lizards, strange to say, are found in Madagascar. This is the more remarkable, inasmuch as we have no evidence yet of the existence in Madagascar of freshwater fishes common to Africa and South America. Again, that remarkable island Madagascar is the home of very singular and special insectivorous beasts of the genera Centetes, Ericulus, and Echinops; while the only other member of the group to which they belong is Solenodon, which is a resident in the West Indian Islands, Cuba, and Hayti. The connection, however, between the West Indies and Madagascar must surely have been at a time. when the great lemurine group was absent; for it is difficult to understand the spread of such a form as Solenodon, and at the same time the non-extension of the active lemurs, or their utter extirpation, in such a congenial locality as the West Indian Archipelago. The close connection of South America and Australia is demonstrated (on the Darwinian theory), not only from the marsupial fauna of both, but also from the frogs and toads which respectively inhabit those regions. A truly remarkable similarity and parallelism exist, however, between certain of the same animals inhabiting Southwestern America and Europe. Thus Dr. Günther has described 15 a frog from Chili by the name of cacotus, which singularly resembles the European bombinator. SOLENODON. Again of the salmons, two genera from South America, New Zealand, and Australia, are analogous to European salmons. In addition to this may be mentioned a quotation from Prof. Dana, given by Mr. Darwin," to the effect that "it is 15 Proc. Zool. Soc., 1868, p. 482. 16" Origin of Species," 5th edit., 1869, p. 454. certainly a wonderful fact that New Zealand should have a closer resemblance in its crustacea to Great Britain, its antipode, than to any other part of the world:" and Mr. Darwin adds: "Sir J. Richardson also speaks of the reappearance on the shores of New Zealand, Tasmania, etc., of northern forms of fish. Dr. Hooker informs me that twenty-five species of algae are common to New Zealand and to Europe, but have not been found in the intermediate tropical seas." Many more examples of the kind could easily be brought, but these must suffice. As to the last-mentioned cases, Mr. Darwin explains them by the influence of the glacial epoch, which he would extend actually across the equator, and thus account, among other things, for the appearance in Chili of frogs having close genetic relations with European forms. But it is difficult to understand the persistence and preservation of such exceptional forms with the extirpation of all the others which probably accompanied them, if so great a migration of northern kinds had been occasioned by the glacial epoch. Mr. Darwin candidly says," "I am far from supposing that all difficulties in regard to the distribution and affinities of the identical and allied species, which now live so widely separated in the North and South, and sometimes on the intermediate mountain-ranges, are removed.”. . . . . 'We cannot say why certain species and not others have migrated; why certain species have been modified and have given rise to new forms, while others have remained unaltered." Again he adds: "Various difficulties also remain to be solved; for instance, the occurrence, as shown by Dr. Hooker, of the same plants at points so enormously remote as Kerguelen Land, New Zealand, and Fuegia; but icebergs, as suggested by Lyell, may have been concerned in their dispersal. The existence, at these and other dis 17 "Origin of Species," 5th edit., p. 459. |