DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
135 
than themselves. Below, there is a narrow, above, a wider and widening tract of 
cartilage, dividing the bony masses of the ear and occiput, which are moderately ex¬ 
tended, wholly ossified, and furnished with a large, wide tegmen tympani ( t.ty .), which 
overhangs the vestibnle (fig. 7) to an unusual extent. These right and left bony regions 
reach to the fore edge of the foramina ovalia, below, which they almost encircle. 
The skull is wide behind, and narrows evenly, with scarcely any bulging up to the 
axils of the ethmoidal region. The covered fontanelle (fig. 6) is very large ; it reaches 
to within a short distance of the foramen magnum, behind, and leaves very little 
tegmen cranii in front. The edges formed by the walls of the skull are straight, and 
those walls have scarcely any “ coping.” The converging and slightly bulging inter¬ 
orbital walls are unossified from the foramina ovalia to the ethmoidal axils; in the 
hinder third of these cartilaginous tracts, the optic fenestra (II.) is seen to be of 
moderate size. The girdle-bone ( etli .) scarcely covers its own territory in front, and 
behind, only ossifies the axillary or pinched part, reaching some way back below ; 
above (fig. 6) it is imperfect, its halves scarcely meeting at the mid-line. 
The nasal region is entirely unossified, there is no prenasal rostrum, and the pro- 
rhinals (fig. 7, p.rh.) are well developed ; the subnasal lamina ( s.n.l .) is very broad, 
and the roof (fig. 6) is of normal width. The external nostrils (e.n.) are only half as 
wide apart as the internal (i.n.). The palato-suspensorial arch is quite normal, both 
in its cartilage and in its bones (jpa., pg.) ; but both the pedicle (pel.) and the quadrate 
(q.c.) are short; the latter is scarcely affected by the quadrato-jugal (q.j.). The Eusta¬ 
chian openings (fig. 7) are rather small, and directed obliquely outwards and forwards. 
The annulus (fig. 8, a.ty .) is a very small crescent, one-third the average diameter. 
The stapes (fig. 10, st .) is large, ear-shaped, and ossified, except at the edges; it has 
a strong apophysis. 
The columella has no inter-stapedial segment, the medio-stapedial ( m.st .) is pistol¬ 
shaped, the large, proximal pedate end not ossified, and the terminal part is a thick, 
short spatulate extra-stapedial (e.st.), with no ascending process. 
The mandible (fig. 8, m.mJc., cl., ar. ) and the hyo-branchial apparatus (fig. 9, c.hy., 
b.h.br., t.hy.) are perfectly normal; the stylo-hyal end (fig. 7, st.h.) is confluent, above. 
The labials ( u.V-.u.l 2 .) and the investing bones are, on the whole, quite normal—that 
is if compared with those of a half-grown Common Frog. The fronto-parietals ( fp .) 
are very wide behind, deficient inside, in front, and on the left side (reversed in fig. 6) 
behind, are unusually developed over the arch of the anterior and posterior canals. 
The parasphenoid (fig. 7, pci.s .) is large and normal, but the vomers (r.) are mere 
films of bone, bordering the inside of the inner nostrils ; they are toothless. 
There are no septo-maxillaries ; the maxillaries (mx.) send up a distinct process to 
articulate with the “manubrium” of the nasal («.), which has the normal conchoidal 
shape, and comes near its fellow, above. 
The pre-maxillary ( px. ) has united, by its nasal process, with the inner upper labial, 
so that this cartilage, like the lower labial, is partly ossified. 
