OCR Text |
Show 1885.] DR. ST. G. MIVART ON THE PINNIPEDIA. 487 process, behind which the bone is rounded. The stylomastoid foramen lies in a deep groove which divides the mastoid from the bulla Ihe meatus auditorius externus is produced outwards, but its lower hp inclines so much upwards posteriorly that the aperture is made to look more forwards than upwards, and the outer end of the lip may be produced a little forwards in front of the aperture. There is a postglenoid foramen. The posterior palatine foramina are situated behind the middle of the palate. The pterygoid has a distinct hamular process. The basis cranii has a surface bent convex downwards between the occipital foramen and the presphenoid. Venous canals traverse the inside of the exoccipitals and open on the inner side of either occipital condyle. The mandible has a distinct subangular process, and the angle is pressed up very near the condyle. The symphysis may be long or short. Dentition:-I. | C. \, P. % M . \=34. Molars, except the first, with two roots. Each upper molar has a principal cusp with one or two accessory cusps behind, and sometimes one in front of it. The lower molars have each a principal cusp with one, sometimes two, accessory cusps in front of it, and generally two behind it. In P. vitulina the hinder margin of the palate is V-shaped, the apex being forwards. The suture between the palatines and maxillae forms a straight transverse line. The teeth are rather large and multicuspidate. In P. grcenlandica the palate has a straight, transverse, hinder margin. There is sometimes a distinct pterygoid fossa. The paroccipital process may form a marked, iiipple"-like projection. The teeth are more simple than in P. vitulina. In P. barbata the maxilla has a swollen outer surface; venous canals open inside the upper margin of the foramen magnum, and a curious ridge runs downwards and forwards across the squamosal and parallel with the hinder root of the zygoma. The meatus auditorius externus looks mainly upwards. The paroccipital process is rather prominent. The palate extends far back, and has an evenly concave hinder margin. The two parietals form a small wedge-shaped process which advances between the hinder margins of the two frontals. Halichcerus 1.-This genus contains but one species, H. gryphus, which inhabits the coasts of Scandinavia and the British Isles. Its palms and soles are hairy, and it has five well-developed claws on each foot, those of the manus being the broader and more curved. There are 15 dorsal, 5 lumbar, 4 sacral, and about 14 caudal vertebrae. In the skull thesame characters are found as those already attributed to Phoca, except that there is a more decided defect of ossification between the ali- and basisphenoids and the pterygoid. Moreover the palatine foramina are much behind the middle of the palate. 1 Fabric. Skrivt. af Naturh. Selsk. i. p. 167, tab. 13. fig. 4; Nilsson, Vet. Akad. Handl. p. 377, tab. 34. figs. 1 & 2 ; Bell, Brit. Quad. p. 278; Gray, Cat. Brit. Mus. p. 33; Schreber, Fortgesetzt Wagner, vii. p. 12; De Blainville, Osteogr. Phoca ; Allen, North Amer. Pimi. p. 682. 32* |