1898.] OSTEOLOGY OF THE IMPENNES. 973 



little, or nothing, of the lachrymal is visible when the skull is 

 viewed dorsally, either in the young or adult. In CatarrJiactes it 

 appears as a narrow ledge outside the nasal. This fact, with some 

 others, serves at once to distinguish the skull of any of the 

 Spheniscidce from that of any of the Colymhidce, in which this bone 

 forms a very prominent, outstanding process. 



The vomer, which is permanently free, is double, but the two 

 halves are united along the anterior half of the inferior border ; 

 the posterior half of the dorsal border of each articulates with the 

 palatine of its own side. 



The palatines underlie the maxillae, and with them extend 

 forward to within a short distance of the tip of the upper jaw. 

 Posteriorly, in the region corresponding with the level of the 

 lachry:nal, the flattened, splint-lilie form becomes greatly expanded, 

 and turns slightly inwards and dorsally. The anterior border 

 assumes a more or less scroll- like form and sends forwards along 

 each half of the vomer a short rod, which apparently never pro- 

 jects beyond the level of the anterior border of the mesethmoid. 

 The outline of the posterior border varies slightly in the different 

 genera and species. 



The pterygoid is rod-shaped, greatly expanded and flattened 

 distally. Like the palatine, it differs slightly in shape, and is 

 accordingly of some help in identifying species and genera. In 

 young birds, and in young birds only, it is continued from the 

 articular end of the palatine, forwards over its dorsal border, in 

 the form of an elongated triangular rod of bone, terminating in an 

 acute point over the extreme postei'ior extremity of the vomer 

 (PI. LXI. fig. 3). Almost immediately behind the posterior end 

 of the palatine, this anterior portion of the pterygoid becomes 

 segmented off from the main body of the bone, and later, a perfect 

 arthrodial joint is formed. Meanwhile, the triangular anterior end 

 has fused with the palatine, making it appear that the joint at the 

 distal end of the pterygoid is a true palato-pterygoid articulation. 

 There is nothing to show that the joint is secondary, and that it is 

 formed by the unequal segmentation of the pterygoid itself. 



In some other forms this pterygoidal segmentation takes place 

 at the level of the posterior border of the palatine, instead of a 

 little caudad of this. 



This anterior segment has been frequently described and figured, 

 in many different groups, by the late W. K. Parker, as a meso- 

 pterygoid. A short time ago I gave a brief description (13) of 

 what seemed to me to be the real significance of this stylet, not 

 knowing then that this had been more or less clearly grasped by 

 Menzbier (11). His description is, however, somewhat meagre, 

 and neither here nor in his figure does he hint at the segmentation 

 of the pterygoid which eventually takes place, though he must 

 have been perfectly well awai-e that such a process occurred. 



As Menzbier has pointed out, the relations of these parts which 

 exist temporarily in the Penguin obtain permanently amongst the 

 Katitse. Dromcuus and Wiea furnish two admirable examples. In 



