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Show 404 MR. W. P. PYCRAFT ON THE [Mar. 21, downwards beyond the level of the tomium, nor extending backwards into the lachrymo-nasal fossas ; interorbital septum perforate. PltOCEIiLARIIDa:. a. Width of the basitemporal plate slightly or not at all exceeding the length of the pterygoid Procellariince. b. Width of the basitemporal plate much exceeding the length of the pterygoid-very slightly less than the distance between the quadrates. Pelecanoidinee. (One genus only, Pelecanoides.) B. Supra-orbital groove with a more or less extensive overhanging ledge, the free edge of which is flattened; temporal fossas represented by shallow semicircular depressions of uniform depth, separated each from its fellow by the broad, quadrangular, shield-shaped roof of the skull; external nares small, opening laterally underneath a broad culmen ; orbitosphenoid completely ossified ; length of the upper jaw greatly exceeding that of the cranium ; basipterygoid processes absent, with the parasphenoidal pneumatic aperture opening above the Eustachian groove in a narrow chink; palatines closely approximated in the middle, line so as nearly to conceal the vomer; palatines relatively short, becoming fused distally with the maxillo-palatine processes, which project downwards far below the level of the tomium ; maxillo-palatine processes large, more or less fenestrated, extending vertically upwards and backwards into the lachrymo-nasal fossa...... DIOMEDEIDJE. Key to the Genera of Procellariinae. GROUP A. Supra-orbital grooves, shallow but very wide, semilunar in shape, almost or quite meeting in the middle line; lachrymal free, with a wide chink between its dorsal border and the frontal; temporal fossae feebly developed or absent. a. Without spine-like wings behind the supra-orbital grooves. a'. Basipterygoid processes absent; maxillo-palatines approaching the mid-ventral line, distinct from the palatines ; supra-orbital grooves separated by a thin linear ridge Oceanites. b. With a conspicuous pair of " wings " behind the supra-orbital grooves. b'. Basipterygoid processes vestigial-in the form of prickles ; maxillo-palatines approaching in the middle line, and partially fused with the palatines. a". Supra-orbital grooves separated by a shallow median groove. Cymodroma. b". Supra-orbital grooves separated by a median linear ridge. Fregetta. c'. Basipterygoid processes absent; maxillo-palatines approximating to the middle line, and quite distinguishable from the anterior ends of the palatine; supra-orbital grooves separated by a thin linear ridge Pelayodroma. GROUP B. Supra-orbital grooves very narrow, excavated out of the free edge of the frontal aud separated by a very broad interorbital median ridge. a. Basipterygoid processes represented by minute prickles; lachrymal free, its dorsal border closely applied to the frontal; maxillo-palatine processes concealed from below by the palatines Procellaria. Halocyptena 1. Oceanodroma. 1 Adult skulls of Halocyptena and Oceanodroma not represented in the Museum collections. |
