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plate of this dermopalatine, or so-called maxillary, bone of Polypterus, 

 would then be naturally accounted for, as would also the intimate 

 connection of the bone, near the middle and at the hind end of its 

 tooth-bearing portion, with the ectopterygoid. Moreover, the auto- 

 palatine, as already stated, lies in part on the dorsal surface of the 

 ectopterygoid and in part on the dorsal surface of the palatal plate 

 of the maxillary, this latter relation being that that an autopalatine 

 and a dermopalatine should have. And if the anterior end of the 

 Teleostean maxillary bone has entirely disappeared in Polypterus, the 

 dermopalatine, or so-called maxillary, would naturally articulate, by 

 its anterior end, with the lateral end of the premaxillary, and, by the 

 dorsal surface of its anterior portion, with the ventral edge of the 

 antorbital, as it does. This is readily seen by a little consideration 

 of my figures of the dorsal surface of the mouth cavity of Amia (No. 3), 

 and it is also there seen that, on one side of the head of the specimen 

 figured, certain of the large teeth of the ptery go-palatine line are fused 

 with the ectopterygoid, while on the other side they are united by 

 their bases to form an independent plate which might as readily fuse 

 with the dermopalatine as with the ectopterygoid, thus prolonging the 

 dermopalatine posteriorly beyond the anterior end of the ectopterygoid. 



The so-called maxillary bones of Polypterus thus probably being 

 the horaologues of the dermopalatines of Amia and Teleosts, they 

 would also be the homologues of a part, or all, of the ptery go-palatine 

 tooth-bearing plates of Selachians and Dipnoids. 



We can now turn our attention to certain other bones of Poly- 

 pterus, the homologies of which have long puzzled anatomists, namely 

 the so - called vomers of Traquair s descriptions , and the unpaired 

 subrostral of Pollard. 



There are, as has been long known, in the mouth cavity of certain 

 fishes, certain mucous folds which, "placed behind the jaws, hinder 

 the outflow from the mouth of the water which has been gulped in" 

 (Stannius, quoted by Pollard, No. 33, p. 399). These mucous 

 folds are called by Pollard the upper and lower vela, but 

 Dahlgren (No. 12), who apparently overlooked the above references, 

 has recently given to them the more appropriate names, maxillary 

 and mandibular breathing valves. This latter author says that he 

 examined over fifty species of fresh-water and marine fishes, and that 

 no single Teleost was found that did not possess the valves. Although 

 the number and the species of the fishes that possessed them is not 

 given, one is led to believe that the distribution in Teleosts is fairly 

 general, and that, accordingly, the valves must have been inherited 



18* 



