458 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 11, 



in the preceding groups ; but in the Procellariidce 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 LaridcB (Loiiffipennes, Nitzsch), the P/o- 

 cellariidcB, the Colymbidce, and the Alcidce. Nitzsch {I. c.) remarks 

 that the pterylosis of the first-named family "approaches very closely 

 to that of the Scolopacinse, and can hardly be distinguished there- 

 from by any character;" and the same may be said of the osteolo- 

 gical and other pecnliarities of the Laridce, which come very near 

 the Cliaradriomorphse. The Alcidce, on the other hand, in their 

 pterylosis and other characters approach the Penguins — es})ecially, 

 as has been noted above, through Alca impennis. The Colymbidce 

 appear to be closely connected on the one hand with the Gulls, 

 and on the other, more remotely, but still really, with the Rails. 



The Procellariidce are aberrant forms inclining towards the Cor- 

 morants and Pelicans among the Desmognathse. 



~r 4. The Spheniscomorph^. 



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 flat- 

 tened 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 trvincated surface, with which the 

 similarly compressed radius andulna 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 Apterodytidce, comprising the genera Eu- 

 dyptes, Spheniscus, and Apterodytes. 



Nitzsch has pointed out that these birds have no remigcs distinct 

 from the other feathers, which are distributed evenly over the whole 

 body, and, though small and scale-like, are provided with an after- 

 shaft. 



