Species of the existing genera Erinaceus, Sorex, Myogale, and Talpa, and of several nearly-allied extinct genera, have been determined from Miocene and subsequent deposits in various parts of Europe, and especially from the lacustrine beds of the Auvergne; and in North America also a few species have been found and referred to genera for the most part almost identical with those still living on that continent. In some instances even the Miocene species appear to be nearly identical with those now inhabiting the same regions.
The principal apparent exceptions to this rule are to be found in a fossil species from the Miocene of the Auvergne, described by M. Pomel under the name of Echinogale Laurillardii (Centetidæ), and two forms described by Hermann von Meyer, as forming a new genus (Oxygomphius), allied to the Bangsrings, from the Tertiary basin of Weisenau, in Southern Germany. But the true position of these fossils is, to say the least of it, exceedingly doubtful; and this is still more strikingly the case with the Eocene American genus Omomys supposed to be an animal allied to the Hedgehogs and the Bangsrings, but which Professor Leidy himself, in describing it, compares with nearly all the types of true Insectivora and with the Opossums.
This last comparison leads us, perhaps, towards the origin of the Insectivora. In the East, the Bangsrings, and notably the beautiful little Ptilocerque, and the curious genus Hylomys, which, again, seems to unite the Bangsrings with the Hedgehogs through the anomalous genus Gymnura, present manifest relationships with the Phalangers, some of which abound in the islands further to the east. From these animals to the true Shrews, many of which abound in the east, is no great step. On the other hand, we have already seen that Brandt recognised Opossum-like characters in his Solenodon, but it must be confessed that these are almost exclusively external. Professor Leidy describes, besides Omomys above referred to, some other fossils from the Eocene of Wyoming, which he seems to regard as Insectivorous in habit, but Marsupial in structure; and the Stonesfield Mammals, although plainly Marsupial, have Insectivorous tendencies, so that the derivation of the type Insectivora from the Marsupials, or at all events the near affinity of the two orders, perhaps at several points of contact, may be looked upon as established.
In the other direction the affinities of the order would seem to be through the Shrews, Hedgehogs, and Centetidæ with the Carnivora, towards which also the curious West African Potamogale seems clearly to point. The Bangsrings, again, show some traces of an affinity to the Lemurs; and Galeopithecus seems almost to constitute a central point of alliances, uniting the Insectivora with the Lemurs and Bats, and further exhibiting, as Mr. Wallace thinks, certain peculiarities which smack strongly of direct Marsupial relations. The relationship of the Insectivora to the Rodentia can hardly be regarded as a true affinity, although the analogies between different types in the two orders are among the most striking phenomena of the kind with which we are acquainted. The type of the Mice and Rats is reproduced by the Shrews, the Squirrels by the Bangsrings, the Porcupines by the Hedgehogs and Tanrecs, the Jerboas by the Jumping Shrews, and the Ondatra by the Desmans; whilst even the highly specialised Moles are reflected among the Rodents by the various species of Mole-Rats. But none of these resemblances indicate affinity, and the Rodent type may be regarded as differentiated from the old probably Marsupial ancestral forms quite independently of the Insectivora.
W. S. DALLAS.
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FOOTNOTES:
[1] πλατύς, flat or broad; ῥινές, nostrils.
[2] κατά, downwards; ῥινές, nostrils.