DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
55 
seen in the skull of small kinds, and bringing into prominence parts that also project 
largely in osseous Fishes. The epiotic region burrowed by the posterior canal (ep.) 
stands out, divergingly, on each side of the great archway, with its transversely oval 
entrance (fig. 4). The anterior canal sweeps round the front; outside it there is 
a great hollow, and then the periotic mass rises over the horizontal canal, this it 
does still more at the edge ( tegmen tympani). The outer margin grows backwards 
into a large terete unossified “ pterotic” ridge ( pt.o.) —the part that is ossified by the 
pterotic bone in Teleostei. The whole structure is, on the whole, bony up to the fore 
margin of the foramen ovale, and these right and left masses are confluent over the 
foramen magnum, but not below (fig. 2); there is a small tract of cartilage in the 
basioccipital region. 
Below, the twin post-aural nerve passages (fig. 2, IX., X.) are wide apart, and the 
antero-external margin of the ear-capsule is bevelled away and covered with a plate 
of cartilage for articulation with the pedicle (pel.). The ear-masses and intervening 
hind skull together make only a third of the whole width at this part; above 
(fig. 1) the pterotic crests (pt.o.) stand further out, where they pass beneath the 
squamosal (, sq .). 
Suddenly in the temporal region the skull is compressed to two-thirds its average 
width, then becomes of a fuller form, and gently narrows again before it spreads out 
into the wings of the ethmoid, opposite the closing in of the cranial trough. 
The optic fenestra (II.) is moderate ; it is margined by cartilage in front, above, and 
below, and the girdle-bone (eth.) has not much more interorbital space than this tract, 
which lies in front obliquely over the bone. There is a small ossified superorbital lobe 
( s.ob.). The cruciform bony mass only reaches in front to the proper morphological 
edge of the ethmoidal territory; all the true nasal region is unossified. The whole 
nasal roof is a winged sub-pentagonal tract, not ending in more than a bud of the 
“prenasal,” and with half its septal part and a headland of its roof uncovered by the 
nasals (fig. 1, s.n., n.r., n.). The outer nostrils (figs. 1, 3, e.n.) are protected by the 
usual inner and outer upper labials (u.P.u.P.). The roof runs forward, narrowing; the 
floor (fig. 2, s.n.) is sub-quadrate, and is finished antero-externally by the curious 
cervicorn angles (Plate 8, fig. 2, and Plate 9, fig. 7, s.n.l.). The septum (s.n.) below is 
very thick in front, and narrows backwards towards the ethmoid bone ; the angles of 
the subnasal lamina behind pass into the large, widely-extended ethmo-palatines which 
are curiously covered with splints, above and below. 
On each side of the bud-shaped end of the septum there is a rather large fenestra 
(Plate 9, fig. 7, s.n.), and in this enlarged figure of part of this region we see the pro- 
rhinal (p.rh.) ; it is very large, sub-flabelliform, and turned (contrary to rule) inwards. 
In this same figure the angle of the nasal capsule, a part derived from the trabecuke, 
is seen to give off a curious retral process ( al.n., s.n.l.) : this is quite normal. 
The whole palato-quadrate arch (pa., pg.) is an immense structure; measured from 
the pre-palatine spike to the end of the condyle, it equals the entire length of the 
