664 ALLIS. [Vor. XII. 
trematic nerve sent to it as the nerve passes outward across it. 
It thus fulfils all the conditions of a suprapharyngeal element, 
and seems certainly to be that element of its arch. If it be 
that element, that part of the hyomandibular that lies in front 
of the facial canal must either be the infrapharyngeal element 
of the arch completely fused with the suprapharyngeal element, 
or an outgrowth of this latter element. Under the former 
supposition the symplectic would be a special outgrowth of the 
infrapharyngeal element ; under the latter it would be that 
element itself. In either case the element would lie below 
the nerve and artery of the arch, as it should, and be connected 
by ligament, or even by fusion, with a part of the next preced- 
ing arch. The adductor hyomandibularis then becomes the 
levator of the hyoid arch, naturally transformed, by the great 
deveiopment of the hyomandibular, into an adductor, and the 
double ligament on the inner surface of the hyomandibular, con- 
necting it with the epihyal and ceratohyal, can be accounted for 
as two remnants of the articular and interarcual ligaments that 
originally bound the epal element of the hyoid arch to the infra- 
pharyngeal element of the next following, or first branchial arch. 
The hyomandibular does not always, in the adult of fishes, 
lie behind the posttrematic branch of the facialis, as it practi- 
cally does in the adult Amia, and as it does in Heptanchus 
(No. 124, Fig. 2) and in Silurus (No. 98, p. 19). In Acipenser 
it lies entirely in front of the nerve (van Wijhe) ; in Spatularia 
either entirely in front of it, according to van Wijhe, or behind 
it, according to Collinge; in Ceratodus behind it (van Wijhe) ; 
in Polypterus between its two branches (van Wijhe and Pollard) ; 
while in Lepidosteus and many teleosts it is pierced by the 
nerve as in Amia. If, then, the hyomandibular be the supra- 
pharyngeal element of its arch, or that element and the infra- 
pharyngeal element combined, it must, in moving upward to 
acquire its articulation at a high level on the lateral aspect of 
' the skull, have passed in some instances in front of the facialis, 
in others behind it, and in others across it or between its two 
branches. 
In the mandibular arch, in Amia, the large median process of 
the metapterygoid fulfils, in its arch, even better than the hyo- 
