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Show 458 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Api*. 11, in the preceding groups ; but in the Procellariidee they become tumid and spongy, and may enlarge so much as to leave a mere cleft in the place of each vomero-palatine space. The angle of the mandible is not recurved. The sternum varies extensively. The hallux is weak, or absent, and (with the exception of the Grebes) the anterior toes are completely, or very largely, webbed. The ratio of the phalanges is as in the preceding groups. This group contains the Laridee (Longipennes, Nitzsch), the Pro-cellariida;, the Colymbidce, and the Alcida;. Nitzsch (I. ci) remarks that the pterylosis of the first-named family "approaches very closely to that of the Scolopacinae, and can hardly be distinguished therefrom by any character;" and the same may be said of the osteological and other peculiarities of the Laridee, which come very near the Charadriomorphae. The Alcidce, on the other hand, in their pterylosis and other characters approach the Penguins-especially, as has been noted above, through Alca impennis. The Colymbidce appear to he closely connected on the one hand with the Gulls, and on the other, more remotely, but still really, with the Rails. The Procellariidee are aberrant forms inclining towards the Cormorants and Pelicans among the Desmognathae. 4. The SPHENISCOMORPH^E. The beak is straight and compressed, the rostrum being, at most, slightly hooked at the tip. There are no basipterygoid processes, and the pterygoids are flattened from above downwards. The maxillo-palatines are concavo-convex and lamellar. The sternum is greatly elongated. The shaft of the humerus is flattened from side to side, and its distal end presents an obliquely truncated surface, with which the similarly compressed radius and ulna articulate-the former altogether with the fore part, the latter with the hinder part of the humeral articular surface. There is no free pollex. The pelvic bones are less firmly connected with the sacrum than in any other birds. The short tarso-metatarsus is perforated by two very large clefts which lie between the middle and the lateral metatarsals. The small hallux is directed inwards or forwards. The ratio of the phalanges is as in the preceding groups. The anterior toes are completely webbed. This group answers to the Squamipennes of many authors, and contains the single family Apterodytidee, comprising the genera Eu-dyqites, Sqiheniscus, and Apterodytes. Nitzsch has pointed out that these birds have no remiges distinct from the other feathers, which are distributed evenly over the whole body, and, though small and scale-like, are provided with au after-shaft. |