660 ALLIS. [Vou. XII. 
e. Mandibular Arch. 
The mandibular arch as generally considered consists of two 
parts, the palatine arch, or palato-pterygo-quadrate apparatus, 
and the mandible; but the mandible and pterygo-quadrate 
represent, quite possibly, the entire mandibular arch, the pala- 
tine part of the apparatus representing or belonging to a pre- 
mandibular arch. To the description of the parts as given by 
Bridge and by van Wijhe I have but little to add. 
At the hind end of Meckel’s cartilage (1/7, Figs. 2, 6, and 7, 
Pl. XX) four ossifications, ossicles a, 4, c, and d of Bridge, were 
sometimes found, and sometimes but three, ossicles 6 and ¢ 
being fused, a faint line almost always indicating the line of 
fusion. The outer, lower corner of ossicle @ had usually a 
slightly different color from the rest of the bone, and there was 
sometimes a faint line between the two portions; but, like van 
Wijhe, I never found the separate dermal scale described by 
Bridge. The canal (mefc) for the ramus mandibularis externus 
facialis, on the inner surface of the ossicle, was always con- 
tinued forward some little distance on the inner surface of the 
articular, and opened underneath the horizontal part of Meckel’s 
cartilage, beyond ossicle 6. Ossicle @ was always capped with 
cartilage, and between the mento-meckelian ossicles (A7J/) of 
the two sides of the head there was always a median, tough, 
semi-cartilaginous piece, intimately connected with the ossicles, 
as if it were the fused, cartilaginous tips of those bones. It may, 
however, be in part a basimandibular, such as White describes 
in Hexanchus and Laemargus (No. 127, p. 60). The hind edge 
of the cartilage of the coronoid process was always seen as a 
line behind the hind edge of the supra-angular, and the process 
itself was always found well developed as a process and not as 
a separate piece, even in specimens 12 mm. in length. In the 
palatine arch the anterior process of the metapterygoid was 
always capped with cartilage, as van Wijhe found it, and there 
was always on the hind edge of the quadrate, between it and 
the symplectic, a small piece of cartilage that escaped his 
notice. 
