570 



5. The vomer of fishes is primarily a bone, doubtless paired, 

 ■which is developed in relation to tooth-bearing plates on the dorsal 

 surface of the mouth cavity; and it was primarily limited to the roof 

 of that cavity. In certain teleosts, however, this tooth-bearing plate 

 has acquired a dorsal limb which may be said to consist of a head 

 and two ascending processes, one on either side ; and these ascending 

 processes are quite certainly formed by the fusion, with the tooth- 

 bearing plate, of the preethmoid (septomaxillary, Amia) bone of either 

 side. When the preethmoids are found as independent ossifications 

 the vomer is without ascending processes. The ascending process of 

 either side, gives articulation, on its dorsal surface, to the ascending 

 process of the corresponding maxillary, as just above stated. 



6. The septomaxillary of the Amphibia and the higher vertebrates 

 is probably represented in fishes by the antorbital bone of Amia, that 

 bone being developed in protective relation to the infranasal portion 

 of the latero-sensory canals. This antorbital latero-sensory bone is 

 found in Polypterus and Elops, as well as in Amia, and is possibly 

 also found in certain of the Siluridae (Pollard). In Polypterus it 

 fuses with the premaxillary to form an infranasal process of that bone. 



7. In Macrodon there is a bone that Sagemehl has called the ac- 

 cessory palatine ; but this bone is apparently developed in the maxillary 

 breathing valve of the fish, and is accordingly not a palatine bone, 

 but the homologue of the so-called vomer of Polypterus. It has never 

 been recognized in any other teleosts. 



8. The palato-quadrate articulations with the ethmoid region of 

 the skull differs somewhat in different ones of the mail-cheeked fishes 

 examined. In Scorpaena and Sebastes there are two of these arti- 

 culations, one with an anterior palatine process of the ethmoid cartilage 

 and the other with the ectethmoid; the lachrymal also articulating 

 with the latter bone. In Cottus the articulation with the ectethmoid 

 is suppressed, the palatine there being bound to the lachrymal and 

 that bone alone articulating with the ectethmoid. In Trigla and Peri- 

 stedion these two articulations are, in principle, much as in Cottus, 

 but there is, in both these fishes, a third and more anterior articula- 

 tion, with the nasal. The lachrymal and palatine are there rigidly 

 bound together, and either the lachrymal alone, or both of the bones, 

 has a sliding articulation with the under surface of the antero-lateral 

 ■corner of the nasal bone. In Dactylopterus this latter articulation is 

 still more pronounced, a special process of the nasal being developed 

 in relation to it. This process lies between the lachrymal and pala- 

 tine, instead of on the outer surface of both those bones, and gives 

 independent sliding articulation to each of them; the lachrymal and 



