264 



canal component of the maxillary. The autopalatine is a small bone 

 and, in the specimen figured, can be said to be a section of an oval 

 cone, its base resting on the ectopterygoid and maxillary bones and 

 its summit, slightly hollowed, articulating with the ventral surface of 

 the antorbital process of the cranium. When the upper jaw spreads 

 these two surfaces slide upon each other, resembling, in this, the cor- 

 responding articulation in many Teleosts. The relation of the auto- 

 palatine and maxillary bones of Polypterus to each other is thus cer- 

 tainly, in this respect, that of the auto- and dermo-palatines of Amia. 

 The "prearticular prolongation of the pterygopalatine cartilage", re- 

 ferred to by Pollard on p. 419 of his work (Xo. 32), and shown in 

 his figure 34, I could not establish in my dissections. 



The anterior edge of the palatal plate of the maxillary lies im- 

 mediately posterior to, or slightly overlaps ventrally, the lateral edge of 

 the palatine process of the premaxillary, the two plates being loosely 

 bound together by a wide band of ligamentous tissue that arises from 

 the anterior edge of the process of the maxillary and is inserted on 

 the ventral surface of the process of the premaxillary. The process 

 of the maxillary, although it has such markedly different relations to 

 the overlying chondrocranium, and the underlying vomer, is, in general 

 appearance, a serial continuation of the palatine process of the pre- 

 maxillary. The palatine process of the premaxillary is, as will be later 

 shown, the probable homologue of the similarly named process of the 

 premaxillary bone of Mammals, but the palatal plate of the maxillary 

 bone is perhaps not the homologue of the palatine process of the 

 superior maxillary bone of Mammals, as will be also later shown. It 

 seems much more probable that it has its homologue in that part 

 of the mammalian superior maxillary bone that marks the position of 

 the floor of the primary nasal chamber, and not in that part of the 

 bone that forms the floor of the secondary chamber. 



The maxillary bone of Polypterus is traversed, through something 

 more than its middle third, by the main infraorbital canal. This canal 

 enters the bone on its dorsal edge, almost exactly in the transverse 

 plane of the hind edge of the palatal plate of the bone, and leaves 

 it on the dorsal edge of its posterior portion, traversing all that part 

 of the bone that forms part of the margin of the orbit. Tube No. 6 

 infraorbital leaves the canal as it passes from the lachrymal into the 

 maxillary. Tube No. 7 leaves the canal as it traverses the maxillary, 

 the surface opening of the tube lying almost directly above the hind 

 end of the tooth-bearing part of the bone. The section of canal that 

 lies between these two tubes, Nos. 6 and 7, is enclosed in what has 



