468 Prof. Reid on the Vogmarus Islandicus. 
texture was prolonged outwards and downwards towards the 
commissure of the lips, running posterior and parallel to the 
body of the intermaxillary. The inferior surface of the thin 
fibrous and superficial plate, with ridges on its external surface 
similar to the opercular bones, covering the sides of the cheeks, 
becomes inseparably blended with the superior surface of the 
lateral fibrous prolongation of the central portion of the superior 
maxillary. The second portion of the superior maxillary consists 
of two fibrous and flexible branches united together, where they 
are connected to the lateral part of the broadest portion of the 
central portion, by a moveable articulation, whence they diverge, 
the one proceeding to join the lower maxilla at the junction of 
its dental and articular portions, the other proceeding forwards 
and downwards to jom the inferior maxilla at its symphysis. 
The bones of the head differed in their structure, but none of 
them contained ossific matter. 
1. Some were composed of a thin, very flexible, fibrous lamina, 
presenting numerous ridges on their outer surface, arranged dif- 
ferently in each. This was the structure of the opercular bones, 
and of two quadrilateral plates, one on the surface of each cheek, 
- placed immediately behind the anterior margin of the imter- 
maxillary bone, united to each other by a portion without ridges 
on its external surface which passed over the dorsum of the 
snout and covered the anterior portion of the nasal processes of 
the intermaxillary. A thin and narrow porous layer of this tissue, 
apparently continued from the opercular hone, passed along the 
upper margin of the orbit. 
2. Some were composed of a fibrous-looking tissue, either 
forming flexible plates and bands without any ridges, or masses 
of greater thickness. The palatine bones and a part of the max- 
illary bones consisted of thin broad plates, of this texture, while 
the body of the sphenoid, the anterior sphenoid, the vomer, the 
intermaxillary, and the central portions of both upper and lower 
maxille were formed of thicker masses of the same texture. The 
lower maxilla contained true cartilage in its interior. 
3. Some were composed of true cartilage enveloped in an ex- 
ternal layer of a fibrous-looking tissue. This was the structure 
of the lateral and posterior walls of the cavity of the cranium. 
4. Some were composed throughout of true cartilage, having 
no fibrous envelope except that constituting the perichondrium. 
This was the structure of the anterior frontals, and the portion 
of cartilage firmly embracing the posterior and middle portions 
of the nasal processes of the intermaxillary. 
The branchiostegous membrane is short, and contains four 
short, very flexible and thin branchiostegous rays, besides three 
others very indistinctly marked placed posterior to these. 
LE eee 
aie 
