PEOr. W. K. PAEKEE ON ^GITHOGNATHOUS BIEDS. 347 



become cartilage ; and then the quadrate can be distinguished as a separate nodule, and 

 the mandible as a separate bar. At that time the maxUlo-palatine process of the embry- 

 onic mandible has a pith of tissue in it more granular than the rest, but no cartilage ; 

 the chick now corresponds exactly to the Menobranchus, save that the pedicle does not 

 pass into the trabecula by continuous cartilage. 



The same process may be traced in the Chelonia ; and in them the free apex of the 

 suspensorium, which, as in the bird, turns forwards as well as inwards, underlying the 

 second and third branches of the trigeminal nerve, is pointed and permanently cartila- 

 ginous, even in the largest Sea-Turtles. That pointed soft end of the suspensorium is 

 the orbital process of the quadrate bone ; in the bird this free end is often broad and 

 spatulate. Here I may remark that I once held the erroneous opinion that this part 

 answered to the orbital process of the Tadpole's suspensorium — a cartilaginous leaf, 

 folded over the outside of the temporal muscle, and only an evanescent structure. 



The "otic process" is only one of two parts that join the ear-sac in the Amphibia 

 (see Huxley on Menobranchus, pi. 30. fig. 1) ; for, besides the proper otic process which 

 coalesces in most Amphibia with the antero-superior region of that organ, the pedicle 

 gives ofi" a facet below, which is well seen in the common Frog, gliding on the smooth, 

 antero-inferior face of the prootic region. 



Now, in birds, the huge otic process of the suspensorium (the head of the quadrate) 

 generally has an outer and an inner fork, and always, save in Ostriches and Tinamous, 

 has two articular facets, even in the Gallinaceous birds and the Parrots, where the head 

 is most imdivided. 



This inner facet does not, however, correspond with the otic facet of the amphibian 

 pedicle, but is a mere fork of the " otic process." 



So far we see that the suspensorium of the bii'd is altogether attached to the head 

 (auditory region) by joints with joint-cavities, whilst in the Amphibia it is attached by 

 bands and joints. 



It is not an easy matter to harmonize the other parts of the palato-mandibular appa- 

 ratus. The ascending process of the Urodela is a mere fibrous band in the Batrachia 

 proper ; and I do not think that Prof. Owen's view is tenable (see Huxley on Meno- 

 branchus, note to p. 189), namely that it answers to the epipterygoid columella of the 

 Lizard. In Lizards and, as I have also discovered, in the Chelonia there are two ptery- 

 goid bones — one the broad flat membrane bone which forms so much'of the posterior 

 palate (the true pterygoid), and the other a rod-like bone lying above the great plate ; 

 this is the columella or epipterygoid. 



In the Chelonia, when recently hatched, this bone is seen to be the separate ossifica- 

 tion of the only part of the pterygo-palatine arcade which acquires any thing like a 

 cartilaginous consistency: it is the postero-superior extremity of the arcade; and its 

 hinder tilted end articulates with the apex of the free pedicle, joining it at right angles, 

 and altogether in front of it ; it cannot, therefore, answer accurately to the Amphibian 



3a2 



