176 MR. W. K. PARKER ON THE OSTEOLOGY 



recently hatched Corvinse, Turdinse, and Sylviinae, and is extremely unlike that of the 

 Galling, Columbinee, PluviaUnae, or Struthioninse. 



The fossa in front of the condyle is well defined in the Hemipodius ; but the anterior 

 and posterior condyloid foramina, and the passage for the " vagus," are very small 

 (Pis. XXXIV. & XXXV. figs. 1, 8, 9). The "basitemporal " region (b.t.) is in size and 

 shape intermediate between that of the Pigeon (PI. XXXVII. fig. 6) and Lapwing 

 (PI. XXXVII. fig. 1) ; and its anterior Hp, below the common opening of the Eustachian 

 tubes, is less pronounced than in the latter, but more than in the former. In the Lap- 

 wing it is really a well-defined process, whilst in certain of the Anatinse it is a sharp 

 style. 



Where the large external ala of the basitemporal ' meets the most anterior spur of 

 the lateral occipital, it bridges over an empty space a little external to the foramen for the 

 " vagus." In this the Hemipodius agrees with the majority of birds. A line or so in front, 

 and mesiad of this space, is the opening of the elegant bony canal for the internal carotid 

 (PI. XXXIV. fig. 1, i.e.), which canal, principally formed by the basitemporal on each 

 side, yet owes some of its substance above to the basisphenoid, and internally (as in the 

 mammals) to the petrosal {prootic). Rathke erroneously terms the symmetrical bones, 

 which in the Snake, Lizard, and Bird invest the internal carotid artery, basisphenoid ; 

 whilst the true basisphenoid, formed originally by ossification of the cartilaginous 

 pituitary floor, he calls " presphenoid " (see Mem. on Balceniceps, p. 280). In ray 

 former paper (p. 316) I spoke of having found the rudiment of a true tympanic bone in 

 the Peahen. Since that time I have dissected a large number of the skulls of growing 

 birds, and find that in one form or another it is a very constant element in the class of 

 birds, oftener, however, existing as a series of ossicles than as one distinct ring^ The 

 bird-class is indeed remarkable for a free development of bony centres, every available 

 structure being in some species converted into bone. We shall see a remarkable in- 

 stance of this in the case of the Tinamou ; but even in such highly organized birds as 

 the Falconina, where the growth is so rapid, and the coalescence of bony elements so 

 complete, there is a profusion of separate pieces, even where their distinctness is most 

 transitory. Let the mere " teleologist," the anatomist of the Sir Charles Bell school, 

 look well to this ! ^ 



' The basitemporal of birds, being very large, ossifies the " lower tympanic lip " of the periotic capsule. 



' Miiller (Physiology of Man, Bal/s transl. 1843, vol. ii. p. 1616) says :— " In young mammiferous animals 

 two other parts " (besides the os quadratum and os zygomaticum) " can be distinguished in connexion with the 

 temporal bone, namely the anaulus tympanicus and the bulla tympani, which Hagenbach could distinguish as 

 separate parts in some mammals." Platner saw " an annulus tympanicus in several birds ; and frogs have also a 

 rudiment of the same part." The ossification of the true internal " bulla tympani " is continuous with that of 

 the prootic in most mammals ; this lower Up of the primary cartilaginous tympanic wall is often absorbed. It 

 is well developed in the Hyrax and Sloth. 



^ I shall not pass by this part of our subject without giving an instance of the prejudices of our anatomical 

 fathers against the results of embryology. 



The great man just mentioned, whose writings have been the joy of every lover of biology, takes occasion, in 



