964 MB. W. p. PYCEAFT ON THE [DeC. 13, 



mesethmoid. It is perforated by an interorbital fenestra, the size 

 of which varies with age. The optic foramen is bounded in front 

 by a median bony bar from the presphenoid, in front of which 

 lies the interorbital fenestra. 



The mesethmoid is a median, vertical, bony plate, in the adult 

 fused with the parasphenoid below and the nasals and frontals 

 above, and merging posteriorly into the orbito-sphenoid. It is 

 greatly thickened anteriorly, and expanded laterally along its 

 dorsal aspect, the lateral expansions curving outwards and down- 

 wards to form the " autorbital plate,"' which encloses a space 

 opening forwards into the lachrymo-uasal fossa. In Ai^tenodytes 

 and Eudyptula only, the postero-superior angle of this antorbital 

 plate is perforated for the olfactory nerve ; in other cases it runs 

 along inside and above this plate and does not perforate it. 

 There are uo turbinal ossifications. 



Only in Aptenodytes does the upper jaw greatly exceed the 

 cranium in length ; for the rest, the length of the upper jaw, 

 from its tip to the ends of the nasal processes, is about equal to 

 the distance from the last point to the cerebellar prominence. In 

 Catarrliactes it is stout and somewhat deflected ; the nasal processes 

 are more or less swollen, attaining their maximum thickness in 

 C. scJilegeli, and their minimum in Meyadyptes antipodum, which 

 closely approaches Pygoscelis. In Pygoscelis the nasal processes 

 are more or less uniform in thickness throughout. In P. pcqma 

 the upper jaw is about i longer than the cranium ; in P. adelke it 

 is much depressed in the middle region, giving the jaw the 

 appearance of being broader across than it really is ; its outline in 

 dorsal profile is, from the tip backwards, convex rather than 

 concave as is usual ; the length of the whole jaw is somewhat less 

 than that of the cranium. In Eudyptula the upper jaw is more 

 slender in proportion to the cranium than in any other genus. 

 In Spheniscus the nasal processes of the premaxilla are greatly 

 swollen, and the space enclosed by the internal and external nasal 

 processes tends to become filled up by bone, and an accumulation 

 of bony matter may run forwards from this along the nasal 

 process of the premaxilla, so as ultimately to considerably decrease 

 the size of the external uares. 



The quadrato-jugal bar in Aptenodytes, Catarrliactes, and Pygoscelis 

 is characterized by a very strongly-marked downward curvature. 

 Descending abruptly from the lachrymal, it straightens out near 

 its middle to run backwards to the quadrate parallel with the long 

 axis of the skull (PI. LX. figs. 1-3). In Spheniscus the curve is 

 comparatively slight, and in Endyptida is barely visible. 



The vomer is free, double, and blade-shaped. The two halves 

 are fused slightly along the antero-ventral border. It articulates 

 on either side with the anterior end of the palatine, which sends 

 forward a bony spur for its increased support. 



The paldiines, anteriorly, form slender rods, running forwards 

 beneath the maxillo-palatiue processes to fuse with the pre- 

 maxilla and maxilla, anteriorly to these processes. Posteriorly, 



