DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
37 
or “ symplectic.” As a rule a short segment is cut off close to the stapes, the morpholo¬ 
gical “ pharyngo-hyalthis has not taken place, at present, in this young Frog. 
The proximal piece is the medio-stapedial (fig. 10, m.st., i.st.), and it is largely ossified; 
the distal piece is not; it is the “ extra-stapedial ” (e.st.) —a peduncidated sub-circular 
disk ; as yet, there is no supra-stapedial band growing up from the inner side.* 
The “ cerato-hyal ” (figs. 7, 9, st.h., c.hy.) is not yet as narrow as it will be, but from 
hanging by its primary joint under the antorbital region, it now is articulated to the 
tympanic floor under the columella and behind the Eustachian opening (eu.), to which it 
now forms the normal boundary as part of the hyoid arch, that is to say, it is behind 
the “1st visceral cleft;” over that cleft, outside, the “ spiracular cartilage” is closing- 
round the membrana tympani so as to form the “annulus” (fig. 6, a.ty.). 
The cerato-hyal band still retains an auriform hypo-liyal lobe (fig. 9, c.hy., h.hy.), but 
the basi-hyal conjugation (h.hy.) is still a tract of simple cartilage running into the 
dilated basi-branchial plate ( h.br.) ; attached to this we see on each side the remains of 
the branchial pouches, and another remnant is seen also on each side of the paired 
hypo-branchial plates (h.br.), which now end in long sigmoid rods (t.liy), the still 
unossified “ thyro-hyals.” 
This is the most instructive intermediate stage of these parts I have as yet 
succeeded in dissecting out; if the figures of these parts be compared with what is 
seen in the larva on one hand, and in the adult on the other, the value of this stage 
will be self-evident. 
The investing bones, the true “parosteal” plates, are nearly all present; those of 
the lower arches have been already described. 
The frontals (fig. 6,f.p., by mistake) are now ,for a while, distinct from the parietals ; 
the latter lie over the paired fontanelles, and the frontals cover the larger space (fo.). 
The nasals, premaxillaries, and maxillaries (n.,px., mx.) are now cpiite normal, the quad- 
rato-jugal (q.j.) is appearing, and the squamosal (sq.) is acquiring a supra-temporal plate. 
Below, the parasphenoid (fig. 7, pa.8.) is quite normal, having ail the hinder processes, 
and there is noy»ro-parasphenoid. The “vomers” (fig. 7, v.) are thin crescentic plates 
notched in front. The palatine and pterygoid bones ( pa.,pg .) are now quite separable 
from the subjacent cartilage, but that is only a temporary state of things in most cases. 
Eighth Stage. —5. Skull of Rana lialecina (N. America) ; If inch long. 
This young Frog was about twice the size of the last, but the species are quite 
distinct; this is the most welcome intermediate form I have found between the typical 
It. temporaria and the gigantic R. pipiens. 
The cranium is much more advanced, but it is still unfinished; in this respect it is a 
good link between the young R. palustris and the adult R. temporaria. In some 
* In Pseudis (“ Cystignath.id.8s”) I shall be able to show two earlier stages of the columella than this 
^Plates 11 and 12), 
