III. Digestive organs.—It is, of course, in the structure of the digestive organs, and par ticularly in that of the teeth, that we find the distinguishing characters of the whole order ; yet so nearly do these organs in the Insecti vora approximate to those in the insectivorous division of the Cheiroptera, that it would not have been possible to separate the two groups, had there been no other important points of distinction. From the insectivorous Quadru mana they are distinguished by the planti grade character of the posterior extremities ; from the bats by the whole structure of the limbs, and from all the true Carnivore by the tuberculated teeth.
There is no inconsiderable difficulty in as signing the various anterior teeth in the Insec tivora to their proper classes. In most of the genera, according to the statement of both the Cuviers and others, there are no canine teeth, and the false molares are very numerous ; but it is in many asses doubtful whether the an terior false molares, as they are termed by these anatomists, be not theoretically canines modified in their form. On this point, how ever, there is no possibility of coming to a satisfactory conclusion, as every one will at last form his own opinion on each case; I shall therefore follow the arrangement of Frederic Cuvier as the most generally known, and, upon the whole, by far the best authority on the teeth of the Alammifera.
The incisive teeth vary greatly in the dif ferent genera. In Mygale, in Scalops, and in Condytura, there is in the upper jaw but a single incisor on each side, which is very strong . and of a triangular form. In the first of these genera it is somewhat curved downwards and backwards, and slightly resembles that of some ltodentia. In &rex (jig. 449) it is also single, very strong, curved, and similar to the canine tooth in the Carnivora, but furnished with a strong tooth-like process posteriorly, appearing almost like a distinct tooth.
In Talpa (Jig. 4-11) there are three superior incisores on each side, which are small with cutting edges, like those of the Carnivora. In Chrysoehlo•is (jig. 450), the single superior incisor is curved, convergent, obliquely trun cate and pointed ; and in Erinaeerts (fig.451) there are three pairs, of which the first is large, nbtuse, and strong, separated by a considerable interval from its fellow, and convergent with it. The others are small and resemble false molares. In Tupaia (fig. 452) these teeth are two on each side, distant from each other, and from the first false molar. The inferior ineisores also vary greatly in their form and number. In Scalups there are two, the first
small, the second larger and resembling in form a canine tooth. In Condytura there are two, rounded in front, flattened behind. In Taps there arc four similar to those of the upper jaw, and in Sams there is one only of a very pecu liar form : it is very long from the anterior to the posterior part, somewhat hooked, pointed, and, in some species, the edge is notched or trifid. There are no true canines, according to the opinion of Frederick Cuvier, in any of these animals, excepting Candytura, Talpa, (in which they exist in the upper jaw only) Ccatencs, and Tupaiu. The first tooth be yond the incisores, considered by Fred. Cuvier as the first false molar in the lower jaw in the mole, is by Baron Cuvier termed the canine. In Cenlcncs these teeth are of the normal form ; and in fact the general arrrangement of the teeth in this genus indicates a marked approach towards the Carnivora. In Condytura the su perior canine is strong and large ; the inferior merely rudimentary.
The molares, as in the other Zoophaga, are divided into false and true. Those of the former class are very numerous and of very various form in the different genera, and the great diversity of number in the molar teeth depends in most cases upon these, the true molares being but three on each side both above and below in all the genera, excepting in Chrysochloris, in which they are 1:1, in Eri naceus, in which they are W, and in Ceutencs 1:1. In Chrysochloris the true molares are very curiously and beautifully formed : they are much compressed from before backwards, of a three-sided form, each of the angles ter minating in a sharp elevated point; thus, in those of the upper jaw, there are two situated externally and one internally, and in the lower jaw one externally and two internally. The whole of the true molares, in all the Insecti vora, are formed of three-sided prisms, either single or double, and surmounted by acute tubercles.
The salivary glands are generally much de veloped in the Insectivore. In the hedgehog the parotids are larger than the submaxillary; the sublingual are placed in two rows, of which the larger is situate nearest to the lower jaw. In the mole these glands are very large; the parotids are of an oblong shape, and the maxillary are formed of several rounded and detached lobes. In Sorex the maxillary glands are of larger size than the parotids, and the latter are situated very low to accommodate the oblique direction of the auditory canal.