HYOMANDIBULA OF THE GNATHOSTOME FISHES 601 
have fused with the ventro-mesial surface of the processus oti- 
cus palatoquadrati. The large posterior opening of the tri- 
gemino-facialis chamber is thus cut into three parts, and the 
rami recurrens and hyomandibularis facialis are said to both 
issue through the dorso-posterior one of the three. What the 
ramus recurrens is I can not make out either from Krawetz’s or 
Greil’s descriptions, but the important point in this discussion 
is that the hyomandibularis facialis issues posterior to the little 
dorsal process (Ia). This little process must accordingly be 
found in that part of the cranial wall of the adult that les an- 
tero-lateral to the foramen faciale, between that foramen and 
the posterior edge of the suspensorium (see van Wijhe’s figure), 
thus forming part of the cartilage that invades and fills up the 
trigemino-facialis chamber and not a part of the lateral wall of 
that chamber, as I concluded in a recent work (Allis 714 ¢). 
Edgeworth (’11), who evidently had not seen Krawetz’s earlier 
descriptions, says (p. 212) that in Stage 42 of embryos of Cera- 
todus ‘‘the hyoid bar extends upwards and inwards towards the 
under surface of the pro-cartilaginous tract connecting the para- 
chordal plate with the auditory capsule, forming the hyomandi- 
bula, the original bar forming the ceratohyal and hypohyal. 
The upper part of the originally pro-cartilaginous hyomandibula 
chondrifies; the lower forms a fibrous tract connecting the outer 
end with the upper end of the ceratohyal. In Stage 48 a down- 
growth occurs from the outer edge of the auditory capsule, ex- 
ternal to the hyomandibular branch of the VIIth, and becomes 
separated, forming a cartilage abutting against the outer end of 
the hyomandibula, and a second more dorsally situated piece is 
subsequently cut off from the auditory capsule.’”? Edgeworth 
further says (1. ¢., p. 2138) that probably no part of his ‘true hyo- 
mandibula’ is preserved in the adult, and that ‘‘The cartilage 
(or cartilages) cut off from the auditory capsule is probably, from 
its relation to the hyomandibular branch of the VIIth, that de- 
scribed by Huxley, Ridewood, Ruge, and Sewertzoff as the ‘hyo- 
‘mandibula.’”’ The vena jugularis is shown by Edgeworth (fig. 
50, p. 223) lying dorsal to his hyomandibula and internal to the 
one or two little cartilages said to have been cut off from the 
auditory capsule. 
