1895.] SKULL OE OSTEOGLOSSUM FOEMOSUM. 303 



alisphenoid (as.) bones at the point where the three are in 

 sutural connection with one another near the antero-superior 

 angle of the auditory capsule (fig. 1). This process is, undoubtedly, 

 the equivalent of the conspicuous ascending or lateral process 

 of the parasphenoid in certain Ganoids, \^hich it also closely 

 resembles in its extensive relations to the anterior wall of the 

 auditory capside, and, more particulai'ly, in its extension so far 

 dorsally as to overlap the sphenotic region — an extension which, 

 so far as I am aware, has no parallel in any other Teleost, 

 although characteristic of such Ganoids as Acipenser, Polypterus, 

 and Amia. The second of the two processes (figs. 1 and 2, j«.a.) 

 is about 13 mm. in length and gi'ows out on either side from the 

 lateral margin of the parasphenoid, immediately ventrad to the 

 root of the ascending process, and tapers to a fi'ee distal extremity. 

 The process is horizontally disposed, at right angles to the long 

 axis of the parasphenoid, or, at any rate, has but a very slight 

 upward inclination from its root outwards, and is furnished with 

 smooth rounded surfaces. This process may be termed the 

 articular process of the parasphenoid. Midway between the roots 

 of the two articular processes, and projecting downwards from the 

 ventral smi'ace of the parasphenoid, there is a mesially situated 

 tubercle of bone (fig. 1, ps.t.) which supports a small cluster of 

 teeth. These are small but variable in size, conical in shape, with 

 pointed crowns, and so arranged that the two largest teeth occupy 

 the hinder margin of the cluster, while about six smaller teeth are 

 closely grouped together immediately in front of them. 



The formation of special articular processes in connection v^dth 

 the parasphenoid is correlated with certain modifications in the 

 mandibular arch, whereby the latter acquires a special articular 

 connection with the former. The metapterygoid (figs. 3 and 4, 

 mt.jjff.) occupies its normal position as the proximal element of the 

 arch. Posteriorly, the bone overlaps the external surface of the 

 inferior half of the hyomandibular (hym.) and the contiguous 

 outer surface of the symplectic (s7jm.); anteriorly, the meta- 

 pterygoid is, in turn, overlapped on its inner surface by the 

 mesopterygoid (m.pg.), while inferiorly it is firmly articulated to 

 the superior margin of the quadrate (q.). The mesopterygoid 

 (fig. 3, m.jjg.) is the largest of the palato-pterygoid series, of 

 which it forms the upper two-thirds. It is somewhat triangular 

 in shape, the apex being directed anteriorly towards the palatine 

 region, while the wider posterior portion overlaps the inner 

 surfaces of the metapterygoid and quadrate bones. Inferiorly, 

 the bone is firmly united to the pterygoid (pc^.) throughout its 

 entire length. The pterygoid (^jc/.) forms the inferior third of 

 the palato-pterygoid series of bones, overlapping the inner 

 surface of the quadrate behind, while externally, and for at least 

 the anterior half of its length, it is rigidly attached to the inner 

 surface of the dentigerous maxilla. A distinct palatine element is 

 either non-existent or entirely cartilaginous, at any rate no trace 

 of a palatine bone could be detected in the specimen examined. 



