AND DEVELOPMENT OF THE BIRD'S SKULL. 133 



The transverse basitemporals (fig. 4, bt) have joined their wings beneath the common 

 Eustachian opening (eu). Above this point the parasphenoid (pas) is seen with small 

 basipterygoid knobs (bpg), and above these and the basitemporals expands on each side 

 into a large trumpet of bone, whose mouth opens into the labyrinthic drum-cavity. 

 These trumpets form the " anterior tympanic recesses," and are lipped by one or more 

 additional (tympanic) ossifications. 



The fore part of the parasphenoid has the shape of a planter's dibble, and ends, blunt- 

 pointed, above the palatine commissure, carrying the hinge mesethmoid on its grooved 

 upper face. The premaxillaries form a triangle whose sides are but little longer than 

 their (ideal) base from side to side, and after forming themselves separately on the 

 spatulate prenasal cartilage, combine at the mid line, not only above but also below, 

 aborting and taking the place of their model, growing even there much more solid than 

 their displaced prototype. 



This is the most Chelonian of all the birds' skulls examined by me ; and knowing full 

 well that the bird's skull, after it has fused its trabecule and acquired a cartilaginous 

 consistency, takes on immediately the most unmistakable Rhynchosaurian characters, I 

 am in nowise surprised to see the Falcon (which shoots upward so high above the 

 Chelonian) in its ascent passing close to and retaining much of the likeness of that 

 less specialized and much less metamorphosed type. That the study of the modifications 

 produced by metamorphosis of the primordial face is of the utmost importance to 

 taxonomists is evident ; and the vomer alone is, in this respect, worth more than all 

 Mr. Garrod's muscles put together. In the Reptilian group the Ohelonia are alone in 

 possessing an azygous vomer; and only a minority of the bird class have the same 

 character. Here, in the Falcon, this bone is not shaped like the proper ploughshare, 

 but like that less common implement the breast-plough, for sod-turning. The blade of 

 this bone is roundly three-toothed, its shaft flat vertically, down-bent in front and lifted 

 behind, and the handle is thick and forked. The blade is wedged behind in the maxillo- 

 palatine harmony, and between the ear-shaped maxillo-palatine lobes. The shaft divides 

 the median nares, right and left ; the two-toothed handle bites the palatine commissural 

 plates ; it is fastened there by a wedge of bone, which has been driven in, as it were, on 

 the right side. This wedge is the right mesopterygoid (mspg). In this type I have 

 found no other vomerine bones. 



The pterygoids (fig. 4, pg) are even less specialized at this stage than those of the 

 Cariama; they are larger relatively, have a less distinct auricular process (epg), and 

 their abortively developed apex only appears on the right side as the mesopterygoid wedge 

 {mspg). 



The only difference between the palatines and those of Dicholophus is their greater 

 shortness ; also whilst the inner ridges end in the Falcon as a short interpalatine spur 

 (ipa), those of the other bird are ragged and formless. In both cases the transpalatine 

 region (tpa) is evenly rounded off, but the outer lobe is scooped below for the palatine 

 muscles. In the jugum of the Cariama the elements once combined ; but I suppose these 

 were then the jugal process of the maxillary, the jugal itself, and the quadrato-jugal. 

 These two latter are not separate, as far as I can see, in the Falcon, which thus 



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