The occurrence of these two animals in the large West Indian islands is an exceedingly remarkable fact in the geographical distribution of animals, when we consider that in the general opinion of zoologists their nearest relations are the Tanrecs of Madagascar, and the Potamogale or River Shrew of some West African rivers. Professor Peters indeed remarks that the circumstance is the less surprising, as a certain type of Iguanidæ, otherwise peculiar to America, is represented in Madagascar, where also are found species belonging to two American genera of Snakes. But this does not explain the phenomenon. Mr. Andrew Murray maintains that the relationship of Solenodon is rather with the Shrews than with the present family, and, in fact, that they are peculiar and gigantic Shrews, which would certainly lessen the difficulty, seeing that there are plenty of Shrews in North America; but his arguments are by no means conclusive. Mr. Wallace, alluding to the occurrence in Europe of fossil remains referred to the Centetidæ, regards this as a case of a type formerly very widely distributed being now broken up, and represented only at or near the two extremities of its greatest range.
FAMILY VI.—POTAMOGALIDÆ.
This family includes only a single species, so that its characters may be indicated as part of the description of the animal itself, namely:—
THE WEST AFRICAN RIVER SHREW.[271]
UPPER JAW OF WEST AFRICAN RIVER SHREW.
(From Transactions, Zool. Soc.)
This was originally described by its discoverer, M. Du Chaillu, as a Carnivore, under the name of Cynogale velox, but as its characters were very doubtful, the name Potamogale, was suggested for it in case of its proving to belong to a distinct genus. The late Dr. Gray described it as a Rodent under the name of Mythomys. Some years later Professor Allman and Professor Barboza du Bocage procured perfect specimens, and proved the animal to belong to the Insectivora, the latter naturalist describing it under the new name of Bayonia velox. Thus within a few years it received no less than three different names.
When the Insectivorous nature of Du Chaillu’s River Shrew was ascertained, it was found to be most nearly allied to the Centetidæ or Tanrecs, with special affinities to the West Indian Solenodons. It is, however, generally regarded as constituting a distinct family, characterised among other things by the less cylindrical skull, the absence of clavicles, the union of the two bones of the shank towards the extremity, the presence of anal glands, and the compressed form of the tail. The teeth, as in the true Tanrecs, are forty in number, but the molars differ considerably in form, as will be seen from the [annexed figures].
LOWER JAW OF WEST AFRICAN
RIVER SHREW.
(From Trans. Zool. Soc.)