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



it receives the posterior extremities of the palatines and the anterior 

 ends of the pterygoid hones, which thus are prevented, as in the 

 Ratitse, from entering into any extensive articulation vrith the basi- 

 sphenoidal rostrum. 



The basipterygoid processes spring from the body of the sphenoid, 

 not from its rostrum, and they articulate vrith the pterygoids very near 

 the distal, or outer, ends of the latter bones. The head of the quad- 

 rate bone is single, as in the Struthious birds (Parker, I. c). 



But the sternum of Tinamus has a great crest, and the coracoid 

 and scapulae have the arrangement and structure usual in the Cari- 

 natse. And though the ischium is not united with the ilium by 

 bone behind the acetabulum, so that the sciatic notch is not con- 

 verted into a foramen by bone, this character is not universal 

 among the Ratitse, and, in Tinamus, a fibrous or cartilaginous bridge 

 does connect the two bones. 



Though the most Struthious of all Cariuate birds, then, Tinamus 

 cannot, I think, be removed from the order of the Carinatse. 



II. In the large assemblage of birds belonging to the Cuvierian 

 orders Gallinse, Grallse, and Natatores, which may be termed Schi- 

 zognathous, the vomer, sometimes large and sometimes very small, 

 always tapers to a point anteriorly ; while posteriorly it embraces 

 the basisphenoidal rostrum, between the palatines. But the latter 

 bones and the pterygoids are directly articulated with one another 

 and with the basisphenoidal rostrum, and are not borne by the di- 

 vergent posterior ends of the vomer. 



The maxillo-palatines are usually elongated and lam-cllar; they pass 

 inwards over the anterior processes of the palatine bones, with which 

 they become united, and then bending backwards, along the inner 

 edge of the palatines, leave a broader or a narrower fissure between 

 themselves and the vomer, and do not unite with it or with one 

 another. 



This Schizognathous arrangement of the palatine bones is ex- 

 tremely well displayed by the Plover, as the accompanyhig figure of 

 the parts in Charadrius phivialis shows. 



The palatine bone (fig. 6, PI) presents an expanded part, which 

 may be called its " body," the inner and outer edges of which are 

 produced into internal and external " lamincB," separated by a lon- 

 gitudinal groove or depression. In this bird the outer lamina de- 

 scends much further than the inner. The free edge of the outer 

 lamina joins the posterior margin nearly at a right angle, and thus 

 gives rise to the "■' postero- external angle." The postero-internal 

 angle of the body of the bone is produced into a " pterygoid 2)ro- 

 cess," which articulates with the pterygoid posteriorly, and with the 

 basisphenoidal rostrum internally. Superiorly the body of the pala- 

 tine bone passes into what may be termed its " ascending jrrocess," 

 which bends round so as to form the posterior boundary of the nasal 

 passage, and ends, on the inner side of that passage, in a slender pro- 

 longation which passes foi-wards and applies itself to one of the forks 

 of the vomer (fig. 8, Vo). 



