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Show 1881.] ANATOMY OF THE ERINACEIDSE. 391 young, but in old animals united, the line of union, however, remaining distinct. The greater and lesser trochanters of the femur are very large; and there is a strongly convex ridge immediately below the greater trochanter, representing a third trochanter. In the teeth the form of the crowns of the first and second molars is especially noticeable : each has five conical cusps-one at each angle, the inner pair nearly as large as the outer, the fifth near the centre of the tooth, connected by an oblique ridge with the bases of the antero- and postero-internal cusps, and separated from both the external cusps (in the unworn tooth) by a deep groove1 (fig. 1). Fig. 1. Crown of first upper molar (right side) of Gymnura raffiesii. Several very interesting points are noticeable in the myology of this species. The panniculus carnosus is thin, and consists chiefly of two pairs of extensive muscles, lining the skin between the anterior limbs and the base of the tail. These two, m. humero-dorsales and humero-abdominales, arise separately from the humerus behind the attachment of the great pectoral muscle, and, passing respectively backwards and upwards and backwards and downwards, soon become attached to and spread out over the internal surface of the integument covering the back and sides behind the scapulae, and the sides and the abdomen behind the umbilicus ; the dorsal pair are inserted into the upper surface and sides of the base of the tail, the abdominal into the under surface and sides of the same part. Added to these, other cutaneous muscles line the integument in front of the fore limbs. Of these the chief are the sterno-faciales, a broad muscular aponeurosis extending upwards on either side of the neck and head from a raphe occupying the centre line of the neck beneath, and connected posteriorly by two pairs of small oblique muscles with the sternum. The facial muscles are well developed. Zygomaticus major and minor arise from the root of the zygomatic arch; and above them a pair of similar but smaller muscles, the levatores ala? nasi (inferior and superior) have their origin from the space between the root of 1 It is especially necessary to examine the crowns of unworn teeth to see the central fifth cusp and this groove separating it from the postero- external cusp ; for in most specimens the central cusp is found worn down, and its base as well as that of the postero-external cusp spread out so as to obliterate wholly or in part the intervening groove; the base of the central cusp then appears as a prolongation of the ridge which, as described above, unites it with the antero-interual cusp. |
