OCR Text |
Show 384 DR. ST. G. M1VART ON THE ARCTOIDEA. [Apr. 21, the lower margin of the nasal pad. The ears are small, rounded, and simple. The palmar and plantar surfaces may be naked or more or less hairy, according to the species. The tail may have (as in the exceptional form L. sendbachii ) a prominent ridge along either side of the tail, and the feet may approximate in form to those of Enhydra. There are 14 or 15 dorsal, 6 or 5'lumbar, 3 sacral, and from 20 to 26 caudal vertebrae. Both the humerus and radius are at their minimum of relative length in the whole of the Carnivora, as also is the relative breadth of the skull behind the orbits. The skull is so long that, though the palate is broad, its length compared with its breadth is greater than in any other Arctoid; and the excess of the length of the pelvic limb over the pectoral is only exceeded by that of Enhydra amongst the whole of the Carnivora. The hyperapophyses on the cervical vertebrae are longer than in any form yet noticed. The are twelve quasi chevron bones to the tail. Each consists of a pair of diverging hypapophyses, which tend, irregularly, to send outmesiad processes below. Each pair depends from the preaxial end of its centrum, beginning at the fourth caudal vertebra. The scapula develops a very strong metacromion process, while the acromion is very slender. The preaxial margin of the scapula is exceedingly convex. The humerus may or may not have a supra-condyloid canal. The supinator ridge is very strongly marked. The ulna develops a distinct process from the middle of its shaft, which process abuts against the radius. The ultimate phalanges of the manus are exceedingly short. The femur has a very strong external trochanteric ridge extending down its shaft. The ultimate phalanges of the pes are of about the same length as those of the manus. To the cranial characters given by Prof. Flower2 may be added the following:-The skull is much flattened superiorly. The ascending process of the premaxilla does not, so far as I have seen, reach the frontal. The maxilla develops a rudimentary preorbital process3. Venous channels traverse the exoccipital, and open on the inner side of either occipital condyle1. The meatus auditorius externus is relatively small. The foramen condyloideum is conspicuous. The mastoid process is concave beneath, and does not descend below the meatus auditorius externus. No ridge connects it with the paroccipital process. The palate is not greatly prolonged behind the last molars. The pterygoids descend below the level of the palate. The internasal septum does not extend back to the hinder margin of the palate. The zygomata, though slender, are rather strongly arched outwards. There are both malar and frontal 1 This is the type of Gray's genus Pteronura. See P. Z. S. 1865, p. 131 1868, p. 66, and Wiegmann's Arcbiv, iv. p. 392 (1839). 2 See P.Z.S. 1869, p. 11. 3 A rudiment of that which is found amongst the Pinnipedia. * Another approximation to the characters of the Pinnipedia. |