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Show 390 MR. w. p. P Y C R A F T O N T H E [Mar. 21, Procellariidas they are unfenestrated, and somewhat resemble those of the Laridas in that they take the form of flattened lamellae. Tuey differ at once from the Gulls, howeArer, in that they are never markedly concavo-convex, and never extend backwards into the lachrymo-nasal fossa. Furthermore, they differ in that they are holloAved out to form the large antrum of Highmore, which is provided with both anterior and posterior apertures. On the palatal surface they may appear, as in the Gulls, in the middle line, between the palatines, as short, somewhat scroll-like processes ; whilst in others, e. g. Priofinus, they are quite concealed by the palatines. In the Diomedeidas the maxillo-palatines and the antrum attain a considerable size. The inner wall is an unfenestrated, vertical, concavo-convex lamella, projecting far back into the lachrymo-nasal fossa. It extends from the level of the posterior narial aperture downwards so as to depend in the median line, considerably beloAv the level of the tomium-as in the Storks ; then turns outAvards and upwards to the tomium to contribute towards the formation of the palatal roof. In this ventral portion is embedded tbe distal end of the palatine. The antrum contains a little cancellated tissue. It opens posteriorly by three apertures-a median and inner, and two lateral ; the former, in Diomedea exulans, extends the whole height of the antrum. In Phcebetria the corresponding aperture is very small. The share contributed by the maxilla to the quadrato-jugal arch cannot be very well made out in the adult, owing to the completeness of the fusion of the different elements. The anterior end of the quadrato-jugal arch, in Oceanites, Cymodroma,'Procellaria, Pelagodroma, Bulweria, and Ossifraga, by a slightly upward direction more or less reduces the size of the lachrymo-nasal fossa, giving it the form, in Oceanites for instance, of a wide chink. In all but Pelecanoides the lachrymal articulates with the quadrato-jugal bar. In Ossifraga this is brought about by means of a triangular bony process arising from the distal end of the jugal. The Vomer, Palatine, and Pterygoid. The vomer, like that of the Ciconiiformes and Anseriformes, is ankylosed with the palatines. In Oceanites, Cymodroma, Pelagodroma, and Procellaria it resembles that of Phaeton (a Steganopode), in that it is cleft in the middle line from behind forwards for the greater part of its length, the two resultant laminae being turned slightly outAvards. Thus, from below, the vomer appears as a tongue-shaped ossification, cleft for about half its length, from behind forwards, and terminating in a more or less decurved point. In Pelecanoides it is somewhat constricted caudad. In the remaining genera of tbe subfamily Procellariidas the vomer is very broad and hastate in form, the sides are raised dorsally, and in Majaqueus, Fulmarus, Thalassceca, Priocella, and Ossifraqa there is a more or less well-marked median dorsal ridge. The tip is more or less pointed and decurved. In Ossifraga the vomer, seen from |
