656 ALLIS. [Vou. XII. 
Its outer edge projects externally beyond those bones. On 
its lower or distal edge, at the inner, lower corner of the piece, 
there is a deep facet which receives the condylar end of the 
ceratohyal, and at its outer, distal corner there is a slight 
enlargement which gives attachment to the articular ligament, 
which binds the piece to the cartilaginous cap or to the sec- 
ondary ossification of the ceratohyal. A slight depression on 
the upper surface of the piece between these two corners indi- 
cates possibly the longitudinal groove found on the dorsal 
surfaces of the epibranchials. At its broader, anterior end the 
epihyal articulates with the cartilaginous interspace between 
the hyomandibular and symplectic. A strong double ligament 
(id.z), arising from the inner surface of the hyomandibular, 
extends along the inner edge of the epihyal, and is inserted, 
one half on the posterior end or edge of the cartilaginous cap 
of the ceratohyal, and the other on the inner surface of that 
cap near its posterior or postero-ventral edge, and beyond the 
cap on the inner surface of the upper end of the lower ossifica- 
tion, the ligament turning abruptly through a right angle at 
about the middle of its course. These ligaments are not the 
articular ligaments of the arch, they resemble much more, one 
or both of them, the interarcual ligaments of the branchial 
arches, and I consider them as such. 
The pharyngohyal, or proximal member of the hyoid arch, 
is undoubtedly the single piece formed by the hyomandibular, 
the symplectic and the interspace of cartilage connecting those 
two bones. The hyomandibular (/7JZD, Figs. 2 and 5, Pl. XX) 
is much the larger of the two bones, and is, roughly speaking, 
rectangular in shape with a large process, the opercular process, 
capped with cartilage and directed upward and backward from 
the middle of its posterior edge. At the middle of the outer 
surface of the bone there is a large opening, the external open- 
ing of the canal by which the facial nerve traverses the bone, 
and immediately below that opening, marking the further 
course of the nerve and its three main branches, there is a 
slight depression on the outer surface of the bone extending to 
its lower edge and widening or separating into two parts as it 
proceeds. Beyond the lower edge of the bone the two depres- 
