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Show 1885.] DR. ST. G. MIVART ON THE PINNIPEDIA. 489 Leptonyx 1.-A genus of one species inhabiting the Antarctic seas. Its hind feet have rudimentary claws, with the first and fifth toes much longer than the others. The skull generally resembles that of Phoca. The premaxillae are widely separated from the frontals, but just attain the nasals, which are anchylosed together and prolonged backwards as a slender process between the two frontals. The infraorbital foramen is of moderate size. There are defects of ossification in the basi- and ex-occipitals and between the basioccipital and basisphenoid ; also between the frontal, maxilla, and palatine, and a very large single sphenopalatine foramen. The anterior nares are neither very wide nor extending far backwards. The alisphenoids and parietals have a rather wide junction. There is a very small true paroccipital process just behind the foramen lacerum posterius, but besides this a vertical ridge juts outwards near the margin of the exoccipital, where it joins the mastoid. The postglenoid foramen is minute, but the condyloid foramen is conspicuous. The palatine foramina open about the antero-posterior middle of the palate. The pterygoid has an outwardly tending hamular process. The basis cranii is convex below as in Phoca. The maxilla develops no preorbital process. The posterior margin of the palate is concave. The mandible is slender, and has no subangular process, but the coronoid rises decidedly above the condyle. The symphysis is rather long. Dentition : - I . | C. \, P. {, M . } = 32. The molars are small, each with a large conical cusp proceeding from a cingulum. There are no distinctly developed accessory cusps except in the last, or last two, lower molars, hut there is a constant tendency to develop an accessory cusp in front of and behind the principal cusp. Ommatophoca2.-This genus contains one species, which inhabits the Antarctic Seas. Here the hind feet are devoid of claws, and the first and fifth toes are much longer than the others. The claws on the fore feet are quite rudimentary. In the skull we here find premaxillae which do not attain the nasals, so that the maxillae help to bound the anterior nares. The nasals are completely anchylosed together, and form a very long isosceles triangle, the long" angle being wedged in between the frontals, while anteriorly the maxillae join the nasals. The orbits are immense, and give a very distinctive appearance to the skull, and the zygomata are "strongly developed and much arched downwards. The infraorbital foramen is rather small. The condyloid foramen is conspicuous. The lower postorbital process is formed by both the malar and squamosal, as in all the genera hitherto noticed. In 1 Phoca leopardina, Jameson Weddell, Voy. South Pole, i. pp. 22, 24, 134. Stenorhynchus Weddelli, Lesson, Mam. 1827, P-.200. •• Leptonyx Weddellii, Schreber, Fortg. Wagner, vu.p 39; Gray, Cat. Brit. Mus. p. 11, Erebus & Terror, pi. 5. . Leptonychotes Weddelli, Allen, N. Amer. Pmmped p 467. 2 Gray Zool Erebus and Terror, Mamm.; Cat. Seals Brit. Mus. p. 13; Schreber's Fortgesetzt Wagner, vii. p. 40; Allen, N. Amer. Pinnipeds, p. 467. |