AND DEVELOPMENT OF THE BIRD'S SKULL. 121 



is a great squarish plate of bone ; as in Caprimulgus, the infero-external angle of this 

 plate has its ossification stopped short, leaving that tract which primarily grew out of 

 the trabecule to conjugate itself with its counterpart process on the palatine bar. This 

 yoke-band is proximally broad and triangular (figs. 1 & 3, ou), and the apex of the 

 triangle, which alone is ossified, grows into two long and slender lashes of cartilage, one 

 of which runs directly across to its endoskeletal symmorph, tying itself to the very apex 

 of the ethmo-palatine crest (fig. 3, epa, ou), whilst the other runs forwards and down- 

 wards, and is attached to the upper surface of the palatine, near its outer edge and 

 opposite the fore margin of the niaxillo-palatine floor (fig. 1, ou, mxp). The strong 

 palatine arch has, notwithstanding its intense specialization, attained the very form 

 which the foremost (trabecular) arch assumes as soon as it can be seen in a vertebrate 

 embryo as clouded bands of granular bioplasm. Here we have symmetrical sigmoid 

 bands, which behind (at then apex) are strongly hooked upwards and inwards ; these 

 bands approximate, coalesce, and then diverge to their free flat anterior ends. Whilst 

 undergoing this junction the trabecule form not only a commissure but a crest ; here, in 

 the palatine arch of Scythrops (figs. 1-3, pa, epa,pg, mspg), each bar grows upwards at 

 the commissure, which forms a semicylindrical trough above (fig. 2), on each side of which 

 the ethmo-palatine processes (trabeculo-palatine conjugational outgrowths) project. 



Each pterygoid (pg) expands in a very ichthyic manner on the fore edge of the 

 quadrate, the expansion being the posterior margin of the subterminal part of the bar ; 

 the real apex is the epipterygoid hook {epg), which is as well developed here as in the 

 Finches. Each pterygoid is a strong bone, sharply keeled both above and below ; leafy 

 above and hooked below, where it articulates with the palatine. It has evidently yielded 

 a mesopterygoid element {mspg) to the upper cartilage of the palatine behind. 



The postpalatine region is vertical, the prepalatine broadly horizontal; the middle 

 part is mixed. The upper edges have united by ankylosis, not, however, without a 

 key-stone, a detached postvomerine piece, and perhaps also a medio-palatine (figs. 

 1 & 2, v,pa). 



The deep thick-edged interpalatine lips, where they embrace the exposed vomerine 

 plate, nearly meet (fig. 1, ipa), so that altogether the lower or hard palate is of great 

 extent and complexity. By far the greater part of the hard palate is due to the larger 

 growth of the median and lateral palatine portions of the overgrown premaxillaries 

 (ppx) ; but there is no little of the maxillary element besides. The proximal or lateral 

 portion of the niaxillo-palatine plates (figs. 2 & 3, mxp) is spongy and of great width ; 

 it rises (fig. 3) up in front of the ethmo-palatine (fig, 3, epa) ; but the heart-shaped 

 median portion, which belongs to both sides, fills in half the space between the median 

 palatine process of the premaxillary and the gap formed by the diverging palatines. My 

 figure (fig. 1) does not show more than the inferior surface of this common median 

 maxillo-palatine mass ; but above, in front of the vertical vomer, it swells out into a very 

 elegant bulb of spongy bone, which is exactly heart-shaped, the base looking upwards. 

 The ankylosed "jugal" bar (j) is strong, and greatly inhooked behind. The small 

 ossified alse nasi with their bony rudiment of a turbinal (fig. 3, aln, ato), form a nostril 

 that looks downwards and backwards. The whole labyrinth is huddled into a small 



