468 
MR. W. K. PARKER ON THE DEVELOPMENT 
the optic nerve (for I. read II.); thence it widens, loses its keel, and becomes grooved 
along its middle below. This bone then trebles its width, and sends out two pairs of 
angular projections, the lesser to support the basipterygoid processes ( b.pg .), and the 
larger farther back to support the vestibular swellings of the ear-capsules (vb.). The 
bone then becomes divided into two sharp styles, wdiich embrace the lower part of the 
basioccipital. The parasphenodd is three-fourths the length of the head ; it forms the 
only floor to the skull in the pituitary region (fig. 3, py. } _pa.s.). 
The bones that invest the skull above, and postero-laterally, will be described in the 
next stage, but partly also in the sections illustrating this. The splints of the 
first arch also will be described hereafter, but there is one which is figured on this 
Plate, namely, the preopercular. This bone (Plate 34, figs. 1 , 2, p.op.) is a very 
narrow, but rather sharp splint, which is applied to, and takes the curves of, the lower 
edge of the suspensorium ; it is the normal splint of the mandibular suspensorium, and 
is more like that of a Frog than that of an osseous Fish. 
The length of the free mandible (Plate 34, fig. 4), as compared with that of the 
palato-quadrate, is as 20 to 19 ; it is, therefore, already a very long jaw. In its hind 
part it is nearly as broad as its pier, and then runs to its end as a somewhat stouter 
rod than the pterygo-palatine above it. 
The condyle ( ar.c .) is cylindroidal, concave as seen from the side, but somewhat 
convex across; there is an ectosteal “articulare” (ar. ) in the broad part near the 
condyle. The angle is scarcely produced ; but in front of the condyle, above, the 
cartilage grows into a pedunculated crescent of cartilage, the coronoid crest (cr.c.) The 
notch between this part and the lessening rod ( mh .) is very deep ; this leafy coronoid is 
convex outside and concave within. The long Meckelian rod [rah.) is gently arcuate 
and pointed at its fore end, where it nearly meets its fellow of the other side. 
This skull is scarcely amphistylic even, much less hyostylic, for the pedicle of the 
mandibular pier is strong and well articulated, but the hyomandibular (Jim.) is feeble, 
and the binding process or symplectic (sq.), feebler still. 
The hyoid pier or hyomandibular (Plate 34, fig. 4, hm.), with its symplectic foregrowth 
(sy.) } is about one-third the size of the palato-quadrate in front of it. The articular 
facet is a long, arched, convex condyle, with scarcely a perceptible neck ; behind it is 
the knob for the opercular; below, this multilobate mass is sinuous, and scooped on its 
inner face to form the oblique condyloid facet for the interhyal. The front margin is 
concave, and the whole bulk suddenly lessens into a sigmoid style, bent first upwards, 
and then downwards, as it runs obliquely forwards to bind inside the hinder angle of 
the suspensorium, which is scooped to receive it. A small oval fenestra is seen in front 
of the middle of the hyomandibular; and around this, below the condyle, there is an 
ectosteal sheath. All but the front fourth of the symplectic also is ossified as a 
delicate shaft-bone. 
The free or postero-inferior part of the hyoid arch is more evenly massive than its 
pier or antero-superior part. The conjugational piece, or inter-hyal (ihy.), is pyriform; 
