DEVELOPMENT OF THE SKULL IN THE URODELES. 199 
These fore- and out-growing horns of cartilage—the ‘‘ sphenotic” angles (sp.o)—are 
here nearly as largely developed as in Stren lacertina (Pls. XX XVIII, XXXIX.); 
they do not take the ossifying matter, but remain soft in front of the prootic bones ( pr.o). 
The same thing occurs in the “Anura,” but lower down in those types, where the 
shortened pedicle articulates with similar tracts (“ basipterygoids”). 
From the cartilages of the occipital condyles, to the “horn” in front, the whole 
occipito-auditory tract is ossified above (fig. 2, ¢.0, pr.o); but below (fig. 3) only a 
crescentic tract of bone clasps the prootic and opisthotic regions; all the main part 
of the floor of the vestibule (vb), the stapes itself (st), and a narrowish tract of the 
tegmen tympani (¢. ty) is unossified. 
But up to the antero-internal edge of the fenestra ovalis the capsule has in all this 
part a second floor of cartilage from the wings of the investing mass (#v). 
The stapes (sf) is a large, oval plate, nearly half as large as the unossified vestibular 
floor; its direction is outwards and a little forwards; and the crescentic bony tract 
which reaches its fenestra behind is the homologue of that bar of the opisthotic 
which in the Sauropsida and Mammalia divides the fenestra ovalis from the fenestra 
rotunda. 
The superoccipital “‘tegmen”’ only stretches forwards to the middle of the auditory 
capsules; they, however, have a narrow selvedge of cartilage which runs forwards into 
the alisphenoidal wall (#). The upper fontanelle runs from this part of the roof 
to the internasal tract; it is a long oval, pinched in somewhat in the postorbital 
region. 
In the whole of the orbital region the inner skull is devoid of both roof and floor. Its 
sides are crescentic in section; for they grow inwards somewhat both above and below. 
From the ascending process of the suspensorium (a. p) to the anteorbital cartilage (¢.pa) 
the wall on each side is ossified; these bones are the sphenethmoids (sp.e); they 
enclose an oblong skull-cavity, with only gently bulging sides; the optic nerves 
(see fig. 7, 11) escape near the end of the wall-bones. 
The internasal cartilage (i.n. ¢) is a flat plate with the outline of an hourglass, and it 
reaches halfway to the front margin of the face. 
The large flabelliform cornua trabecule (c.¢r) which it binds together, enclose by 
their inner projections three fourths of a circle, bounded behind by the internasal band. 
The angles of these dilated cornua are rounded; the edge reaches from the palatine 
plate of the premaxillary to the internal nostril (?. 7), a large, oval, oblique passage 
between the vomers and palatine on the inside, and the unossified membrane in the 
maxillary region on the outside (fig. 3). 
Above (fig. 2, na), the nasal roofs are crescentic shells of cartilage, with their pointed 
horns looking forwards and inwards; the narrow nasal bones (m) only cover their 
inner horn. 
Behind these cartilages, on the lower plane, the ear-shaped ethmo-palatines (é.pa) are 
