271 



internal to the premaxillary, the latter bone thus, even here, lying 

 morphologically anterior to the maxillary, as it naturally should if it 

 belongs (Gegenbaur) to a still more anterior arch. 



In Amiurus the maxillary bone is said by Mc Mukrich (No. 23) 

 to be a much elongated rod that projects at right angles to the side 

 of the skull, and has lost all the usual relations to the gape of the 

 mouth. The base of the bone is said to lie between the premaxillary, 

 in front and below, and the palatine, behind, and it is the palatine 

 bone and bone 4 of Mc Murrich's descriptions that together form the 

 bony support of that part of the lateral edge of the mouth of the fish 

 that lies posterior to the premaxillary. The maxillary bone of the fish 

 has some sort of relation to the maxillary tentacle, but just what this 

 relation is I cannot make out from the several descriptions and re- 

 ferences to it. Mc MuRRiCH says, in one place, that "The maxillae 

 are specialized for the support of the long maxillary tentacles", but, 

 in another, that "At the base the bone forms a complete sheath for 

 the cartilage which supports the maxillary tentacle". In a later work 

 on this same fish Mc Murrich (No. 24) says that the base of the bone 

 "encloses the proximal part of the tentacle", that the "osseous support 

 of the long tentacle is the maxilla", and that "the relation of the 

 maxilla to the tentacle was probably secondary". 



Among other Siluroids, Pollard says (No. 33, p. 401) that in 

 Trichomycterus and Callichthys the maxillary tentacles "are supported, 

 through the intermediation of a small maxillary bone [os labial Cuvier, 

 adnasaP) Mc MurrichJ, on the prepalatine piece of cartilage". In 

 Auchenaspis the same author says (p. 402) that the maxillo - coronoid 

 tentacle "is borne by the maxilla, which articulates with the prepalatine 

 piece" ; and this prepalatine piece of this fish is said to have ossified 

 so that only apophyses of cartilage are left. There is thus, in Auchen- 

 aspis, a maxillary bone which articulates with a separate, independent, 

 and partly ossified palatine piece, and the raaxillo-coronoid tentacle of 

 the fish is borne by the maxillary bone. This, when compared with 

 the conditions found in Amia, would seem to indicate that the ten- 

 tacle is simply the maxillary fold (maxilla) prolonged, and Cuvier is 

 said by Pollard (No. 33, p. 405) to have so defined "the principal 



1) This is evidently either a typographical error or a marked mis- 

 conception of the bone, for although Mc Mukrich says that the adnasal 

 "lies at the base of the maxillary tentacle", he further says that it "is 

 really a continuation of the infraorbital chain". It cannot, accordingly, 

 be the homologue of the Teleostean maxillary, and it is quite probably 

 the homologue of the antorbital bone of Amia (No. 3, p. 438). 



