DEVELOPMENT OF THE SKULL IN THE BATKACHIA. 
613 
pedial ” (m.st.), and suddenly dilates into a large plate, like the blade of a spade ; this 
is the “ extrastapedial ” ( e.st .). This plate, which has some calcified patches, sends 
upwards and backwards from its inner face a band of cartilage which coalesces with the 
tegmen tympani ; this is the “ suprastapedial ” ( s.st .). In the Grey Frog this part does 
not coalesce above ; in the Bull-frog it does. The relation of the extrastapedial flap to 
the membrana tympani is shown in the side view (fig. 7, e.st., m.t.) ; it is imbedded 
amongst a rather loose gauze of fibres, which arise from the shelving outer surface of the 
thick-edged crescentic, cartilaginous “ annulus ” (a.t.). This part was developed, 
originally, from a little trifoliate cartilage which, in the larva, bridged over the space 
between the elbow of the mandibular pedicle and the tegmen tympani ; it detaches 
itself and becomes crescentic*. 
The portio dura passes over the “ medio- and inter-stapedial ” bar, but when its fibres 
come across the “ annulus,” they pass beneath it ; in the larvae of Daetylethra ( infra 
Plates 56 & 57) the early conditions of the annulus and tegmen are so remarkable, that 
even Professor Huxley himself was doubtful (before he ascertained for me the course 
of the portio dura nerve) as to whether these were not the rudiments of the huge 
columella of that species. 
There remain to be described the investing bones ; these are faintly shown in the 
figures for the purpose of a better display of the fundamental cranium : they are very 
similar to those of the Frog (“ Frog’s Skull,” plate ix.). Above, the principal bone is 
the fronto-parietal (fp-) each double bone keeps distinct, by a suture, from that on 
the other side. The nasals (n.) are large convex plates, subtriangular above, and sending 
down a process to join the face, where the maxillary, palatine, and pterygoid meet. 
Below, the great dagger-shaped parasphenoid ( pa.s .) has the basitemporal haft with 
a point at the end of each process, and not abruptly truncated as in the Frog ; these 
processes are nearly as large as the blade. Each vomer (fig. 4, v .) is a 4-sided bone, 
concave below, toothed in front, and emarginate externally. The palatine (fig. 4, pa.) 
is a thin knife of bone, passing from the outer part of the cartilaginous bar to the edge 
of the parasphenoid, almost transversely, but a little deflected towards its inner end ; 
this and the following properly belong, not to the parosteal, but to the ectosteal series. 
The pterygoid (fig. 7, pg.) is a curious obliquely triradiate bone, convex below, 
where it wholly invests the cartilage, and concave above, where it leaves it somewhat 
exposed at the end. Its arcuate front spur reaches the transverse palatine bone, its 
inner spur runs up beneath the pedicle and aborts the metapterygoid, and its external 
spur runs backwards, forming a strong splint to the inner face of the quadrate. A bony 
sickle (g.j.), representing in one piece the ectosteal plate of the quadrate and the qua- 
drato-jugal of the Sauropsida, is strongly attached by its broad end to the quadrate outer 
face, is overlapped by the handle of the squamosal (sg.), and has its convex ridge 
attached, in front, to the jugal process of the maxillary (mx.). The great hammer- 
* See “ Frog’s Skull,” plates v.-vii., where it is lettered, both in its attached and its free stage, as s.li.m. ; for 
I was deceived by it, and took it for the rudiment of the “ columella auris.” 
