36 MR. GARROD ON THE NASAL BONES OF BIRDS. [Jail. 7, 



passes in front of the posterior terminations of the nasal processes of 

 the prEemaxillse. 



But several birds present a very different condition. In Grus, for 

 example, the posterior contour of the osseous external nares, instead 

 of being rounded, as in holorhinal birds, is apparently formed by 

 the divergence of two straight bars of bone, which enclose an 

 angular space between them. These two processes evidently cor- 

 respond to the two anteriorly directed cornua of the holorhinal skull 

 described above ; but they appear in many cases to be so different in 

 density, and the outer one joins the body of the bone so abruptly, 

 that it seems at first sight to be an independent ossification ; how- 

 ever, I have no reason to believe that such is the case. As in 

 holorhinal birds, so in those under consideration, which may be 

 termed schizorhinal, the internal process of the nasal bone runs 

 forwards along the outer border of the nasal process of the prae- 

 maxilla, and the outer descends free to join the maxilla. In these 

 birds there is considerable variation in the manner in which the 

 almost detached outer of the two nasal processes joins the body of 

 the bone. In Numenius, Hcematopus, and many of the Limicolse 

 they proceed directly upwards and expand, becoming slightly fanned 

 out where they join the rest of the bone by a straight transverse 

 line. In Ibis and Grus they are of uniform size from end to end, 

 whilst in the Auks, and to a less degree in the Gulls, at its origin 

 the process is slightly curved, being directed outwards for a short 

 distance, and after that straight downwards and forwards. 



In most schizorhinal birds, a transverse line joining the extreme 

 posterior point of one external nasal aperture to the similar one of 

 the opposite side is situated behind the posterior ends of the nasal 

 processes of the praemaxilla ; but in some of the short-beaked, broad- 

 mouthed species of the class it is situated in front of them. Such is 

 the case in Pterocles and Syrrhaptes ; and this peculiarity renders it 

 at first sight uncertain whether they are schizorhinal at all ; but as 

 every intermediate condition may be found between the strictly 

 schizorhinal skull of the Columbidee proper, and the very similar 

 but less strongly marked skull of Pterocles, there is no real reason to 

 doubt that the modification only depends on the great breadth of 

 beak in the latter bird. The curious development of the superficial 

 nasal turbinal bone of Pterocles is also a Columbine character, as is 

 also the great length of the inner of the two nasal processes, which, 

 in a manner quite unlike that of the Gallinse, extends on each side 

 for a long way forwards under the premaxillary nasal splint. 



Subjoined is a list, alphabetically arranged, of the genera iu which 

 I have observed the schizorhinal arrangement : — 



Schizorhinal Birds. 



Alca. Charadrius. Gallinago. 



Anous. Chionis. Glareola. 



Anthropoides. Dromas. Grus. 



Arctica. Eurypyga. Hcematopus. 



Cataractes. Fratercula. Ibis. 



