DEVELOPMENT OF THE SKULL IN THE BATKACHIA. 
645 
curvature of the columella is equal to a quadrant ; it is, however, oblique, for the large 
outer face of the leafy extrastapedial is well seen in the upper view, and only partially 
on the lower (figs. 1 & 2, e.st.). Seen from within (fig. 7) the leaf seems to be cordate', 
but its lobes overlap the stalk (see fig. 1), and closely approach each other, except at 
the base. 
The extrastapedial of Bufo vulgaris (Plate 54. figs. 7, 8, e.st.) is small and inelegant 
compared to this, whose exemplar is the leaf of a water-lily. But the setting of this 
plate is equal to its form ; around it is the attenuated annulus tympanicus (compare 
Plate 58. figs. 2 & 3, a.ty., with Plate 59. figs. 1, 2, 3, 4, 7, a.ty.), whose upper deficiency, 
much less than in Bufo , is supplemented by two true tympanic bones, not single, as 
in the Mammal, but divided, as in the Bird (Plate 59. figs. 3, 7, 8, ty a ., ty b .). The upper 
tympanic bone (fig. 3, ty a .) lies on the junction of the medio- and interstapedial bars *. 
The infero-posterior segment, or element of the second postoral arch, has dwindled 
to a mere tape (Plate 58. fig. 5, and Plate 59. figs. 2, 3, 4, cJiy.), whereas it was massive in 
the extreme (Plate 58. fig. 4, c.hy.). It does not reach the typical Batrachian place of 
suspension, namely, behind and below the otic process of the mandible, but is suspended 
thereto by a ligament, almost a quarter the length of the bar. This ascent of the cerato- 
hyal is about equal to that of a Urodele. 
The cerato-hyal is but little wider in the middle ; it is gently hooked round below, 
meeting its fellow at the basal bar. All these are nearly of the same breadth and 
strength ; all are fused together, and the median part is still continuous with the basi- 
branchial ( b.br .). The anterior part of the barred branchial pouch (Plate 58. fig. 1) is 
converted into a persistent functionless branchial (Plate 58. fig. 5, hr. 1, 2) of great 
length and breadth. The apiculate anterior part of the two bars is bound together by 
the confluent broad basibranchial ( b.br .) ; then there is an oval fenestra, and behind this 
a small hypobranchial band passes inwards, on this side and on that, and from the con- 
fluence of these there grows a wider band, which speedily becomes trifid. These three 
processes grow directly backwards : the middle is short and unossified, an oval lobe ; 
whilst the paired processes are the huge, long, little-diverging “ thyro-hyals,” the repre- 
sentatives of the cornua majora of the Mammal — not formed, as in that group, out of 
the first branchial arch, but rather being a modified condition of the hypobranchial 
region of the third and fourth. The larynx (lx.) lies between these bars, which have 
each an osseous shaft, as in the Frog (“ Frog’s Skull,” plate x. figs. 1 & 2, pp. 171, 
172)+. 
Together, the external and internal auditory structures form a large, double labyrinth, 
with the narrow cranial tube between the right and left regions. 
* In the inverted figure (7) the whole columella is shown dislocated, to display its inner face, and drawn from 
under the upper tympanic. 
t Professor Huxley contends with me as to the truth of this, remarking that the thyro-hyal structures are 
median in the Urodeles. They are so in them, and yet only submedian in the Anura ; the changing of the 
distal part of a rod into a basal piece is a very simple and common process. 
