No. 3-] THE OSTEOLOGY OF THE PIGEONS. 493 



other, and spread out over the upper surface of the broad abut- 

 ment afforded by the ethmoid ; but they do not cover it entirely, 

 as the supero-lateral margins of this bone are seen upon either 

 side in the "nasal slit." The fused prcmaxillaries present 

 long and slender processes ; the narial apertures (or bony nos- 

 trils) being long, capacious clefts between them laterally (see 

 Figs. I, 3, and 4, PI. A, px.). They fuse also with the bones 

 with which they come in contact, as the nasals and the maxil- 

 laries. Faint sutures, however, may often be discerned among 

 them, even in fully adult pigeons. 



A maxillary is completely absorbed or fused with the pecul- 

 iar maxillo-palatine process that it gives rise to anteriorly ; 

 while its backward-extending rod for the zygoma is curved 

 downwards and is exceedingly slender. A considerable inter- 

 val divides the maxillo-palatines from each other in the middle 

 line, and either one of these elements is found to be an elon- 

 gated osseous roll, spo7igy within, perfectly smooth tvithout, and 

 fitting snugly in among the maxillary proper, the palatine, and 

 the nasal process of the premaxillary, with all of which it fuses 

 in the adult bird. Extending backwards and downwards from 

 the maxillary bone, the especially slender zygomatic bar has 

 upon its proximal end a minute peg-like process with which to 

 articulate with the outer side of the quadrate. Both /z^;^^/ and 

 quadrato-jugal elements are found in this hinder end of the 

 zygoma, and their suture lines may often be made out even in 

 skulls of adult birds. 



Either quadrate has a double mastoidal head ; two elongated 

 trochleae upon the condylar process, that are placed lengthwise 

 directly in a transverse line with respect to each other; and 

 finally the orbital process is well developed. Several of these 

 bones at the base of the skull are pneumatic, and their air holes 

 are easily made out in each case. In the quadrate it is situated 

 on its posterior aspect, directly between the mastoidal heads ; 

 in the pterygoid it is on the anterior side of the bone, close to 

 the quadratal head ; and in the palatine it is on the outer sur- 

 face of the bone and close to the pterygoidal head. Other 

 parts of the skull in Ectopistes are also pneumatic. 



Coming to the mandible, it is seen to be of the V-shaped 



