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Show 1026 MR. W. P. PYCRAFT ON THE [Dec. 19, The Premaxilla, Nasal, and Lachrymal, The naso-premaxillary region of the upper jaw bears a strong superficial resemblance to the Alcidae on the one hand, and certain genera of Penguins on the other, e. g. that of Megaeudyptes. It may readil.y be distinguished from the former by the form of tbe nostrils, which are schizorhinal iu the Alcidae ; from the latter, apart from the rest of the skull, it would be difficult to distinguish it. _ The nasal, in the adult, both in the Colymbi and Pygopodes is completely fused with the premaxilla and frontals. In the Divers it is, furthermore, fused with the outer border of the lachrymal. It is not deeply cleft caudad, the form of the external narial apertures being holorhinal; they are also, by the way, in the dried skin pervious, there being no nasal septum. The lachrymal is a fairly large bone in the Colymbi, with a peculiar notch in the posterior border of its free end; in the Podicipides, as elsewhere remarked (pp. 1024, 1031), it shows signs of degeneration. The Maxillo-jugal Arch. The maxilla, in the adult of both Grebes and Divers, is indis-tinguishably fused with the premaxilla. Tbe maxillo-palatine processes are Charadriiform in type, closely resembling those of the Alcidae, being leaf-shaped, and in the Colymbi more or less fenestrated. The antrum is very shallow. They are widely separated in the middle line, and the palate is therefore schizo-gnathous. The form of these processes rather closely resembles that of the smaller Tubinares, e. g. Pelagodroma, Procellaria, but differs markedly from that of the larger forms, such as Puffinus for instance. In these, it will be remembered, the maxillo-palatine processes do not extend backwards into the lachrymo-nasal fossa, and are hollowed out to form a spacious antrum of Highmore. The anterior end of the maxillo-jugal arch does not trend upwards to meet the lachrymal, as in many Procellariidae, but the lower limb of the lachrymal in the Colymbi is very long, so much so as nearly to touch the bar, and thus to completely shut off the triangular lachrymo-nasal fo^sa from the orbit. The greater part of this arch is made up by the quadrato-jugal bar. The Vomer, Palatine, and Pterggoid. The vomer in the Colymbi appears to be free throughout life; in really adult or advanced Podicipides it fuses with the palatines'. In the Colymbi it somewhat closely resembles that of the Diomedeidse, appearing knife-shaped from below and provided with a pair of lateral wings along its dorsal border. It differs from this type, however, in that it lacks the conspicuous dorso-ventral curve. Its dorsal aspect is trough-like, and posteriorly lodges the anterior end of the parasphenoidal rostrum. In the Podicipides it is knife-like, and lacking the lateral wino*s, |