DEVELOPMENT OF THE SKULL IN THE BATEACHIA. 
631 
in and filling up all the space between it and the flat mandibular pedicle (t.ty., pd.). 
Taking this anterolateral start, it runs forwards, equal to the capsule in breadth and 
in length — a huge wavy ribbon of cartilage. In front it is not distinct, as cartilage, 
from a foot-shaped flap, which, added to it, almost doubles its length ; for the toe-end 
nearly reaches the hyoid condyle (fig. 5), and overlaps the orbitar process (fig. 4). Just 
outside the front of the capsule the cartilage is punched, as it were, into a neat, round, 
nearly perfect hole, in which is imbedded a gland (1 the “ thyroid,” tr.g.). This preaudi- 
tory growth is the homologue of what I took to be the upper part of the hyomandibular 
(“ Frog’s Skull,” plates v., vi., vii., s.h.m.). It behaves somewhat differently, however, for 
the anterior part does not coalesce with the mandibular pier, which, here, has no elbow ; 
and the foot part answers to most of the little bar in the Common Frog. The broad 
proximal part is a huge awning to the tegmen, and the pedate part is the early condition 
of the annulus. The two parts show, at present , no sign of past or promise of future 
separation : they will separate, as we shall see (see Plate 58). Comparing these parts 
with what we see in the adult (Plate 59), with its huge columella with two bony shafts, 
ending in a huge heart-shaped leaf of cartilage, the extrastapedial, it seemed to me 
(and until the nerves were worked out by him, Professor Huxley sympathized with me 
in the matter) that here, if anywhere, we had the supero-anterior segment of the hyoid, 
the true hyomandibular, with its symplectic distal part. 
The course of the “ portio dura ” beneath this awning directly contradicted this view, 
and a careful comparison of the various stages showed me how the pedate flap changed 
slowly into the cartilaginous tympanic ring. It became evident that, as in our native 
Batrachia, the “ columella ” is very tardy in development. I could not find it at all 
chondrified in the largest young (4th stage, Plate 58. figs. 2 & 3), although these were 
outwardly metamorphosed, save for the presence of a considerable tail (see Dr. Gray’s 
illustration, Proc. Zool. Soc., Nov. 8, 1864, p. 463, fig. 2). 
6. The labial cartilages. — In these, as in the other parts, the connecting-tracts have 
chondrified, and fused together parts morphologically diverse. Moreover, the right and 
left moieties have lost all distinction (Plate 56. figs. 4, 5, u.l.). This double labial (right 
and left in one) is equal in breadth and more than equal in transverse extent to the two 
cornua trabeculse. Its fore edge is greatly concave ; its hind edge is obliquely grafted 
on to the shelving fore edge of the internasal part of the trabeculae ; but a fissure 
appears on each side, and then the two bands diverge from each other (u.l., c.tr.). Out- 
side these is a sudden notch, but not an end to the labial ; for this ribbon runs, as a 
gradually attenuating thread of true cartilage, to the very extremity of a long labial 
tentacle, so long at this stage that it reaches to the end of the abdominal cavity 
(figs. 1-3). This answers evidently to the persistent “ maxillary tentacle ” of the 
Siluroid fishes, e. g. Clarias capensis, Arms rita, &c. 
I see no traces of any other tentacles than these. The Siluroids have two or three pair of 
them, or even more, the lower lip also possessing them. In Dactylethra the lower labials 
(fig. 6, l.l.) are smaller than in the common, and much smaller than in the Bull-frog. 
