DEVELOPMENT OE THE SKULL IN THE BATKACHIA. 
651 
The convex margin of the subocular fenestra ( s.o.f .) is the concave margin of the 
mandibular pier, which, in front of this, passes again into the trabecula, and then grows 
a little forwards into an auriform lobe : the conjugational part is the ethmo-palatine (see 
figs. 5 & 6, e.pa.) ; the free lobe, in front, is the prepalatine spur (pr.pa.), — in the early 
stage of a Batrachian embryo this is the “ prenarial ligament ” or “ lamina,” as the case 
may be. On this foremost bifid lobe the dilated end of the trabecular “ cornu ” rests ( c.tr .). 
Outside the rudimentary palatine cartilage there is a large semicircular notch, and the 
lobe bounding this outside is a rounded condyle, the condyle of the quadrate ( q ), on 
which the scooped upper face of the free mandible hinges (fig. 4, ar., mk.). On the 
upper face of the quadrate angle (Plate 61. fig. 1, or.p.), the outer muscles of the cheek 
run to be attached to its outer side, and the temporal muscle runs under and within it ; 
it does not attempt to make a bridge across to the ethmoidal region of the trabecula, 
for it is scarcely as much developed as in Bactylethra (Plate 56. fig. 4, or.p.). The 
sinuous facet for the hyoid arch (fig. 3, hy.c.) is close behind the condyle of the 
quadrate, but it lies further outwards (compare figs. 3 & 4, the latter of which shows 
the arches that have been removed, ar., mk., and c.hy.). 
But, unlike other types, the outer part of the quadrate sends a process, outwards and 
backwards, the lower face of which process is faceted for the evanescent hyoid bar ; the 
process and the facet are as evanescent as the bar, which soon wholly disappears. 
Between the lobe for the hyoid and the last and longest of these lobes there is another 
semicircular notch, and from thence a long finger of cartilage grows backwards and 
slightly outwards. This long lobe rests its end beneath the tegmen tympani ( t.ty .), at 
its foremost third ; it is a little longer than the flat inner process, and its rounded end 
is free ; this is the otic process ( ot.p .). This spur is quite similar to what may be 
seen in the adult Proteus and the young (half-grown) Axolotl ; it is far more developed 
than its counterpart in the fourth stage of Dactylethra (Plate 58. figs. 2, 3, ot.p.). The 
eyeball rests upon the broad central part of the mandibular pier, a little to the outside 
(Plate 60. fig. 3, and Plate 61. fig. 1, e.). Altogether, this fixed part of the mandible is 
very much advanced for so young an embryo. 
The free part of the arch (fig. 4, ar., mk.) is an elegant bow, moderately bent, and 
whose lateral “ horns ” bend gently backwards to where they are fused. This fusion of 
the free mandibles is rare in the lower types ; it is perfect in some Mammals ( cc Pig’s 
Skull,” plate xxxi. fig. 7 a, mk.s.); at present there are no “ inferior labials,” and I question 
their existence separate from the fused ends of Meckel’s cartilages. The upper surface 
of the articular region (ar.) is cleanly scooped out to roll on the rounded condyle of the 
quadrate. There is no bony investment to the mandible, as there is none to the chon- 
drocranium generally. 
The early visceral cartilages seen in the under face (fig. 4) have much in common : 
they are all united together by fusion at the mid line ; but the last four pairs of bars 
also catch each other’s edges, and unite, both above and below, to some extent. The 
second postoral arch (c.hy.) is large, more than twice as large as the rest; it is longer 
4x2 
