274 PEOr. W. K. PAEKER ON THE STEUCTUEE AND 



pinched-in in the middle by the ingrowth of the cochlear pouches {chl). The large 

 pre- and ^os^auditory nerve-passages (v, ix, x) are very similar, and besides a pair of 

 passages for veins, there is a small posterior hole, right and left, for the hypoglossal 

 nerve (xii). In the fore half of the hind skull the cartilage is burrowed on its lower 

 face by the converging internal carotoid arteries {i.c), which pass into the skull through 

 the pituitary space on each side of the apex of the notochord. This space is at present 

 filled with the gland-like racemose mass of the pituitary body {py) ; one of the " acini " 

 is much larger than the rest, and is in the centre of the mass. 



The lingular processes of the trabecule {tr) end as solid rod-like bars with bulbous 

 and somewhat inturned ends, some distance outside the pituitary space. These rods 

 converge, are separated by a space only equal to their own width, and then become flat 

 and vertical, and run straight forwards. The space between them is filled by the solid 

 rounded end of the elongating intertrabecular bar {i.tr) ; this bar is, indeed, a vertical 

 plate, the orbito-nasal septum, and ends, in front, in the rounded (prenasal) rostrum 

 {p.n) ; this median element grows lower down than the lateral bars. 



The trabeculEe only run up to the front third of the intertrabecula ; they thicken a 

 little, become thinner again, and are then enlarged into a solid wedge-like mass ; these 

 lobes are the "• cornua trabeculse," the " super-vomerine lamina? " of my paper on the 

 Fowl's Skull {op. cit. pi. 83. fig. 4, s.v.l). The occipital and nasal roofs (PI. LXIV. 

 fig. 9, s.o, na) are now chondrified ; the former are bounded by the auditory capsules 

 (au), which appear on the upper surface, right and left. 



b. Visceral Arches. 



The mandibles and their piers are rapidly increasing in size (PI. LXIV. figs. 8, 10, 11, 

 and PI. LXVIII. fig. 10, q,mk,ar); and the hyoid arch (PI. LXVIII. figs. 10, 11) is 

 now complete, and bears the same relation, in size, to the mandibular arch, that the 

 branchial arches, proper, in Ganoid and Teleostean fishes do to the hyoid and the 

 mandibular; but this sudden arrest of the postmandibular arches is attended with 

 new specializations of the lessened elements ; and the tracts of cartilage that do appear 

 serve every purpose of the new functions to which they are dedicated. 



The quadrate (PI. LXVIII. fig. 10, q) has now developed an angular projection from 

 the fore corner of its huge otic process {ot.p) above ; the " orbital process" also is much 

 more developed. The condition of this process here is very instructive ; it is a well-formed 

 rudiment of both the "pterygoid cartilage" {pg.c) and the "pedicle" — such a pedicle 

 as exists in Triton and Salamandra, where the articular part of the pedicle does not 

 coalesce with the basis cranii, but is merely a facet on the inside of the " ascending 

 process." Here the ascending process (a.p) is arrested as a flat triangular flap ; in the 

 ordinary Lizard it is a distinct, long, terete rod of cartilage ("Lizard's Skull," pi. 41. 

 fig. 3, e.p//), which afterwards ossifies as the " epipterygoidean columella." In Hatteria 

 (Giinther, Phil. Trans. 1867, pi. 1. figs. 3, 4) it is a large flat piece ; in both it has 



