— 145 — 



There is no BASISPHENOID bone, as just above stated, nor is there an ORBITOSPHEXOID. 



The ALISPHENOID is bounded by the proötic ventrally, the frontal dorsally and the sphenotic 

 postero-laterally. Its anterior edge forms the dorsal half of the large orbital opening of the brain 

 case, this edge of the bone being, because of the flattening of the hind wall of the orbit, presented 

 almost directly mesially. There is no indication of a parasphenoid leg to the bone. On the dorsal 

 half of the inner surface of the bone there are two brace-like thickenings, the larger one of which 

 underlies the antero-lateral corner of the postepiphysial interspace of cartilage, while the other forms 

 the dorsal end of the anterior wall of the labyrinth recess. The mid-brain recess lies between the two 

 braces. The anterior edge of the bone is either notched, or perforated by a small foramen which 

 must transmit the anterior cerebral vein, though this vein was not traced in the dissections. Not 

 far from the ventral edge of the bone a small opening leads into a canal which traverses the bone and 

 transmits that branch of the ophthalmicus lateralis that innervates the terminal organ of the supra- 

 orbital canal. 



The SPHENOTIC is bounded by the alisphenoid, proötic and pterotic, and gives support, 

 on its dorsal surface, to the frontal and postfrontal bones. Its dorso-lateral corner comes to the level 

 of the dorsal surface of the secondary skull, and has surface markings similar to those on the adjacent 

 dermal bones. Between it and the proötic there is a deep facet for the anterior articular head of the 

 hyomandibular, while, posteriorly, between the sphenotic and the pterotic, there is a small dilatator 

 fossa. The bone is traversed by a canal for the ramus oticus facialis, as in Scorpaena. 



The DILATATOR OPERCULI, it may here be stated, is found in anterior and posterior 

 portions which are separated from each other by the complete fusion of a suprapreopercular bone with 

 the hyomandibular. The anterior portion arises in the dilatator fossa, is fibrous, with but few muscle 

 fibers, and is inserted on the suprapreopercular and the adjoining portions of the hyomandibular. 

 The posterior portion is muscular, arises from the posterior surface of the suprapreopercular and the 

 adjoining portions of the hyomandibular, ventral to the opercular process of that bone, and has its 

 insertion on the opercular. The fusion of the suprapreopercular with the hyomandibular thus cuts 

 the originally continuous muscle into two portions. 



The PROÖTIC is bounded by the alisphenoid, sphenotic, pterotic, exoccipital and basioccipital 

 bones, its ventral edge being overlapped externally by the parasphenoid. The opisthotic does not come 

 into bounding relations with it. The mesial process of the bone inclines strongly upward and corresponds 

 to the postpituitary portion, only, of the processes of Trigla and Scorpaena. The lateral corner of 

 the anterior edge of the process is perforated by the foramen for the nervus abducens. The anterior 

 edge of the body of the bone is perforated, as in Trigla, by a large opening which is the facialis 

 opening of the imperfectly enclosed trigemino-facialis chamber. This chamber forms a deep recess 

 on the orbital surface of the proötic, and from it four foramina usually lead into the cranial cavity. 

 Two of these foramina are large, one of them lying directly dorsal to the other and being separated 

 from it by a delicate bar of bone. The other two foramina are small, one of them lying immediately 

 dorsal to the dorsal one of the two large foramina, and the other one anterior to the line of Separation 

 between the two latter foramina. The dorsal one of the two large foramina transmits the nervus 

 trigeminus and ramus buccalis lateralis, the ventral one transmitting the nervus facialis. The small 

 foramen dorsal to the trigeminus foramen transmits the ramus ophthalmicus lateralis, this foramen 

 being sometimes fused with the trigeminus foramen. The other smali foramen transmits the ciliaris 



Zoologica. Heft 57. 19 



