390 ME,, w. p. PTCRAFT ON THE [Mar. 21, 



Procellariiclss they are unfenestrated, and somewhat resemble those 

 of the Laridae in that they take the form of flattened lamellfe. 

 Tiiey differ at once from the Gulls, however, in that they are 

 never markedly concavo-convex, and never extend backwards into 

 the lachrymo-nasal fossa, riu-thermore, they differ in that they 

 are hollowed 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. Priojlnus, they are quite concealed by the 

 palatines. 



In the Diomedeidse 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 uarial aperture 

 downwards so as to depend in the median line, considerably below 

 the level of the tomium — as in the Storks ; then turns outwards 

 and upwards to the tomium to contribute towards the formation of 

 the palatal roof. In this ventral portion is embedded the 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 Phoebctria 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, 

 Gymodroma, 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 qnadrato-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, Gymodroma, Pelago- 

 droma, and Procellaria it resembles that of PJiaeton (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 outwards. Thus, from below, the vomer appears 

 as a tongue-shaped ossification, cleft for about half its length, 

 from behind for\^ ards, and terminating in a more or less decurved 

 point. In Pelecanoides it is somewhat constricted caudad. In the 

 remaining genera of the subfamily Procellariidie the vomer is very 

 broad and hastate in form, the sides are raised dorsally, and in 

 Majaqueus, Fidmams, Thalassceca, Priocella, and Ossifraga 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 



