— 161 — 



The head of the vomer is bent downward and thickened, as in the other fishes of the group, 

 this thickened portion forming a broad transverse but untoothed surface whieh extends across the 

 anterior end of the ventral surface of the bone. The lateral ends of this dental but untoothed ridge 

 are concave or flattened, and give origin, on either side, to a very short but stout vomero-palatine 

 ligament which has its insertion on the internal surface of the anterior end of the body of the palatine. 

 Beginning immediately lateral to the dental ridge, at the anterior edge of the vomer, a slight ledge 

 extends postero-laterally across the ventral surface of the bone to its bind edge, and that small part 

 of the ventral surface of the bone that lies antero-lateral to this ledge lies at a slightly deeper level 

 than the remainder of the surface. The anterior edge of this little surface of the bone is rounded, 

 fits into a deep groove on the internal surface of the base of the maxillary process of the palatine, 

 and gives articulation to that bone; the tall posterior wall of the groove on the palatine fitting against 

 the little depressed surface on the vomer and the edge of this part of the groove abutting against 

 the ledge on the vomer and so limiting the inward swing of the palato-quadrate apparatus. The 

 rounded articular edge of the vomer is continuous with a similar edge on the pedicle of the ectethmoid, 

 the latter bone apparently participating slightly in the articulation; this articulation thus certainly 

 containing the anterior ethmo-palatine articulation of the other fishes of the group, and apparentlv 

 representing that articulation alone. Posterior to the articular groove on the palatine, the dorsal 

 edge of the latter bone abuts against the ventral surface of the pedicle of the ectethmoid and is bound 

 to it by tough fibrous tissue, this contact apparently representing the posterior ethmo-palatine artic- 

 ulation, here practically suppressed. 



The ECTETHMOID has a somewhat diamond-shaped and strongly convex external surface, 

 the dorsal and lateral surfaces of the bone being inclined at more than a right angle to each other, 

 and the lateral edge of the bone being, in consequence, directed ventro-mesio-posteriorly. The 

 posterior edge of the bone is curved and slightly concave, is presented postero-laterally, and forms 

 the anterior portion of the margin of the orbit. The mesial edge of the bone forms two sides of the 

 diamond-shaped outline of the bone. The posterior one of these two sides is straight, is presented 

 postero-mesially and suturates with the frontal; the anterior one suturating in its posterior half 

 with the nasal, while its anterior half is occupied by a deep, oblong incisure which forms the ventro- 

 antero-lateral boundary, and part of the dorso-postero-mesial boundary of the nasal opening. The 

 bent-under lateral edge of the bone is slightly concave, the concavity arching over the lateral edge 

 of a tall and flat articular eminence which begins at this edge of the ectethmoid and extends mesially 

 and slightly posteriorly along the ventral surface of the bone. This eminence projects ventro-mesially 

 and gives articulation to a facet on the dorsal edge of the lachrymal. 



Beneath the curved external, and evidently purely dermal portion of the ectethmoid, the 

 deeper portion of the bone extends into the cartilage of the antorbital process, forming a sort of 

 pedicle to the external portion. The pedicle is directed ventro-mesially, and is partly in synchondrosis 

 with the median remnant of the antorbital cartilage, and partly in sutural contact with the vomer 

 and parasphenoid. The anterior surface of the pedicle is deeply hollowed to form part of the bounding 

 wall of the nasal pit, its posterior surface being less deeply hollowed to form part of the anterior wall 

 of the orbit. In the mesial edge of the pedicle there is an incisure which, with the adjoining cartilage, 

 forms a foramen which transmits the olfactory nerve from the orbit to the nasal pit. 



The ORBIT is deep and low, with curved but nearly transverse anterior and posterior walls, 

 formed, as usual, by the concave posterior surface of the ectethmoid and the anterior surface of the 



Zoologica. Heft 57. 21 



