OSTEOLOGY OF THE PENGUINS. 393 



iuence ' is well developed, and raised as a vertically elongated 

 dome on the brain-case proper. Most peculiar is the occipital crest 

 •or ridge ; it being not especially well defined in Ajjteoiodytes, 

 though strong enough to bound the occipital area. In S]3Tien- 

 iscus so remarkably deep are the crotaphite fossa: at the sides 

 of the cranium, that not only the occipital crests stand out as 

 free laminte of bone, but the aforesaid crotaphite fossae even 

 appear to undermine the very plane of bone that in most birds 

 ■constitutes the occipital area itself, and this is continuous with 

 the cristal portion. As pointed out by Watson, the basis of 

 these free laminae of bone in Penguins like Spheniscus are found on 

 the line dividing the brain-casket from the cerebellar prominence, 

 but in Aptenodytes, where the crotaphite fossffi are quite incon- 

 spicuous and very shallow, the occipital ridges are found away 

 from the cerebellar prominence, and, as in many other water- 

 birds, occur upon the cranium proper. At the lateral aspect of 

 the skull the post-frontal processes are povverfvilly developed, 

 and point directly downwards, while, upon either one, the 

 superorbital glandular depression t-erminates upon the upper 

 ■side. Less prominent is the squamosal process, though it is 

 amply evident enough to bound the valley running between 

 it and the post-frontal apophysis. 



A very large vacuity occupies the posterior two-thirds of the 

 interorbital septum in Aptenodytes ; it is smaller in Spheniscus 

 demersus ; and, usually, still smaller in some other species of 

 this genus, as S. minor. Considerable variation is seen in the 

 lacrymal hones of Penguins, for in Aptenodytes the superior 

 portion of one of these comes in contact with the imder side 

 of the nasal, as well as with the outer lateral edge of the same 

 bone, and the frontal consequently can be well seen upon 

 superior aspect of the skull. Now, in Spheniscus demersus this 

 articulation is upon the nether aspect of the naso-frontal bones 

 •entirely, and thus conceals the lacrymal when the skull is 

 looked at upon direct superior aspect. 



The middle portion of a lacrymal is more or less contracted, 

 but it spreads out again below, in order to make, in all the 

 genera, an articulation upon the upper side of the zygoma. In 

 S. demersus the central portion of either lacrymal is pierced by 

 •a large foramen, while in Aptenodytes this is absent, and the 



