288 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
process passes forward and upward to touch upon the alsphenord. 
Upon the inner surface of the bone, not far from the base of this 
process, is a foramen leading into a canal which traverses the 
hyomandibular from above downwards and backwards, opening on its 
posterior surface a little above the posterior inferior angle. This 
canal contains the R. hyoideo-mandibularis facialis. On the outer 
surface is a flattened ridge overlying this canal, immediately behind 
which is the articular knob for the operculum, and extending forward 
at right angle to it is a ridge for the attachment of muscles. The 
hyomandibular articulates above with the péerotic, sphenotic, and 
alisphenoid ; in front with the metapterygoid, and slightly with the 
quadrate ; below with the symplectic cartilage and the preoperculum ; 
and behind with the operculum. 
2. THE SYMPLECTIC 
Element does not appear to ossify. It is represented by a cartilage 
contained partly within the hyomandibular and partly within the 
quadrate, and filling up the space between these two hones. 
3. Tue Hyorp 
May be described as consisting of five portions, as follows :— 
(a) The interhyal is represented by a small knob at the extremity 
of the arch which is connected by ligament to the inter- and preoper- 
culum, the hyoid thus being fixed at its upper extremities without 
articulation with the symplectic. 
(b) The epihyal is the upper triangular portion of the arch, 
separated from the succeeding portion by a deep notch above and 
below, and by a usually well marked articulation. 
(c) The ceratohyal is the longest portion of the arch ; broad and 
flat above, it becomes contracted towards its anterior extremity and 
again expands for articulation with the hypohyals. Both the cerato- 
hyal and epihyal bear branchiostegal rays on their lower borders. 
(d) The hypohyal is united with its fellow of the opposite side by 
ligament. The bone so denominated in Amiwrws is not simple, but has 
usually connected with it one or two accessory nodular bones, the 
number frequently varying on opposite sides in the same individual. 
(e) The wrohyal is an impair bone extending back from the junc- 
tion of the hypohyals. Anteriorly it is partly divided into two 
rounded portions, from the extremities of each of which a ligament 
passes forward uniting it to the hypohyal. Behind is a thin flattened 
