404 ME. Av. p. PYCRArT ON THE [Mar. 21 , 



doT^-nwards beyond the levol of the tomium, nor extending backwards 

 into the hichrymo-nasal fossse ; interorbital septum perforate. 



PllOCELLARIIDiE. 



a. Width of the basitemporal plate slightly or not at all exceeding the length 



of the pterygoid Procellariina. 



b. Width of the basitemporal plate much exceeding the length of the 



pterygoid — very slightly less than the distance between the quadrates. 



Pelecanoidhics. 

 (One genus only, Pelccanoides.) 



B. Supra-orbital groove with a more or less extensive overhanging ledge, the free 

 edge of which is flattened ; temporal fossfe represented by shallow serai- 

 circular 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 pai-asphenoidal pneumatic aperture 

 opeuinf'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 masillo-palatine processes, 

 which project downwards far below the level of the tomium ; maxillo- 

 palatine processes large, more or less fenestrated, extending vertically up- 

 wards and backwards into the lachrymo-nasal fossa DiOMEDEiDiE. 



Key to ilie Genera of Procellariinse. 



Gkoup a. Supra-orbital grooves, shallow but very wide, semilunar in shape, 

 almost or quite meeting in the middle Hue ; lachrymal free, with a wide 

 chink between its dorsal border and the frontal ; temporal fossje feebly 

 developed or absent. 



a. Without spine-like wings behind the supra-orbital grooves. 



a'. Basipterygoid jDrocesses absent ; maxillo-palatines approaching the 

 mid-ventral line, distinct from the palatines ; supra-orbital grooves 

 separated by a thin linear ridge Oceanitcs. 



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. 



Freffetia. 



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 Pelagodroma . 



Group B. Supra-orbital grooves very narrow, excavated out of the free edge of 

 the frontal and separated by a very broad interorbital median ridge. 



o. 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 '. 



Oceanodroma, 



* Adult skulls of Halocyptena and Oceanodroma not represented in the 

 Museum collections. 



