THE SKULL IN THE WOODPECKERS AND WRYNECKS. 5 



canal is three fourths closed. The commissure above is peculiar : each bone has a car- 

 tilaginous selvedge ; these meet together, coalesce, and in front endostosis takes place, 

 so that a dagger-shaped wedge of bone divides the sides of this arch. This is the " medio- 

 palatine" (Plate I. fig. 2, and Plate III. figs. 5 & 6, m.pa). The " ethmo-palatine " 

 region is prcemorse, having no long spur as in most birds. The secondary parts of the 

 palatine arch equal in interest those formed directly in the primary bar : these are the 

 maxillary, palato-maxillary, and jugal. The maxillary (Plate I. fig. 2, and Plate IIP 

 fig. 6, mx) is most developed in this species ; but the maxillo-palatine plate is merely a 

 small suboval outgrowth, joined to the main bar by a wide isthmus; it is convex above 

 and concave below. 



This process is far apart from its fellow, and grows out of the narrow maxillary bar 

 nearer to the posterior than the anterior end ; both of these regions are long narrow 

 styles ; and the bone grows outwards most where it gives off the inner plate or " maxillo- 

 palatine." The essential nature of the maxillary is well seen here as a long bony 

 bar applied to the outside of the second praeoral arch — long, because of the very pro- 

 gnathous face of the bird ; in this case its palatine portion is scarcely more developed 

 than in the Teleostean fish. The posterior splint, the jugal, is of the normal size, and, as 

 in many of the arboreal birds, has no separate quadrato-jugal attached to it. Besides the 

 " maxillo-palatine " process, there is, as in certain of the " Coracomorph^," Cardinals, 

 Buntings, &c, a " palato-maxillary " bone. This, however, gives a peculiar asymmetry 

 to these buds ; for it only appears on the left side (Plate I. fig. 2, p.moc) : in the young 

 bird it is a small wedge attached to the inner side of the main maxillary, some distance 

 in front of the " maxillo-palatine process." Thus we see that the single mammalian 

 maxillary may be represented by three bones in the bird : the "postmaxillary," which 

 I first observed in the young Emu, is about as common as the distinct palato-maxillary ; 

 the " septo-maxillary " belongs to the first prseoral arch *. 



The newly fledged Green Woodpecker presents an excellent subject for determining 

 the morphological meaning of the parts composing the nasal labyrinth. These have 

 always to be worked out with the prceovsl arches, with which they are even more inti- 

 mately blended, by metamorphosis, than the postov&l with the ear-sac. A vertical section 

 of the head, made a little to the left of the axial cartilage, is very instructive (Plate I. 

 fig. 3). This section takes in the whole length of the trabecular arch from its apex, 

 now involved in the basisphenoidal mass (b.s), to its azygous extremity, the shrunken 

 prsenasal (p.n). The " parasphenoid " has its "rostrum" still distinct ; but the broad 

 hinder portion has been ingrafted on the apices of the trabecule and the squared end 

 of the "investing mass," to form that composite cranio-facial bone, the " basisphenoid." 

 The bony matter has reached to the " optic commissure " and the sides of the deeply 

 cupped " sella turcica." A fine drawn obliquely through the middle of the circular 

 optic foramen (2) and the oval interorbital space (i.o. s) would exactly divide the facial 

 from the cranial elements, so soon, by metamorphosis, wrought into a common mass, 



* In the " Fowl " paper (note at bottom of p. 773) I have spoken of the " septo-maxillary " as " distinct in no 

 bird." Only ■within the last few years have I found the true centre ; and it is very commonly present, not, however, 

 in the subject of that paper, the Fowl. 



