Professor Huxley, about thirty years ago, proposed to classify birds by the form of the bones of the palate. In the skull of the Hawk, it will be seen that two bones lying in the front region of the palate are fused with each other in the middle line, and to the type of skull which is thus characterised the name ‘desmognathous’ was given. It is found not only in the Hawks, but in a quantity of other birds; for instance, in the Stork tribe, and in the Hornbills and Toucans. The second form of skull distinguishes the gallinaceous birds; in them the two maxillo-palatines remain unconnected, and the palate is therefore in a way cleft; this is termed the ‘schizognathous’ skull. In the finch tribe there is a slight modification of this, called, from the Greek word for a finch, ‘ægithognathous.’ In these birds a median bone, called the vomer, from the fact that the bone to which it corresponds in the human skull is shaped somewhat like a plough-share, is truncated in front, instead of tapering, as it does in the schizognathous skull of the common fowl. There is a fourth variety, which marks out the Ostrich tribe and the American Tinamous, in which the two pairs of bones called the pterygoids and palatines do not, as they do in the types of skull that have been hitherto considered, reach the middle line of the skull, but are kept off from it by the vomers, which extend backwards. The term ‘dromæognathous,’ or emu-like, is applied to this form of skull. If the back of any bird’s skull be examined, it will be noticed that just below the great hole or foramen, through which the medulla passes to join the spinal cord in the canal of the vertebral column, is a rounded, rather kidney-shaped boss. This is the occipital condyle, by means of which the skull articulates with the first vertebra. If you look at the same region in a mammal, you will find that there are two of these, one on each side, though also below the foramen magnum. This is one of the many points of structure that distinguish a bird from a mammal and ally it to the reptiles; but it must be remembered that in some reptiles there is a commencing division of the single condyle into two. The Vertebral Column.