263 



scriptions of the Characinidae (No, 37) and Cyprinidae (No. 38), neither 

 describes, nor indicates in any way the existence of, a palatine process 

 of the premaxillary. 



The so-called maxillary bone of Polypterus forms, as Traquair 

 has said, the larger part of the dentary margin of the upper jaw, 

 and a considerable part of the lower margin of the orbit. The ventral 

 edge of its anterior half, approximately, is nearly straight, and is lined, 

 its full length, with a single row of strong teeth. The posterior half 

 of the bone is an untoothed dermal plate that extends upward and 

 backward behind the eye. On the mesial edge of the anterior half 

 of the tooth-bearing part of the bone there is a thin, projecting, pa- 

 latal plate, not described by Traquair, which is wider at its free 

 mesial edge than at its lateral base. This palatal plate of the maxil- 

 lary bone lies directly upon the thin cartilage that forms the lateral 

 portion of the floor of the nasal chamber, and is so loosely bound to 

 it that it slides upon it when the upper jaw is moved. The posterior 

 three-quarters, approximately, of the vomer, excepting its mesial 

 margin, rests directly upon the oral surface of this palatal plate, and 

 is firmly and immoveably bound to it, so that the vomer follows all the 

 movements of the maxillary. The anterior end of the ectopterygoid is 

 similarly bound to a narrow posterior portion of the ventral surface 

 of the palatal plate of the maxillary, the ectopterygoid and vomer 

 here slightly overlapping each other, the vomer lying ventral to the 

 ectopterygoid, the reverse of what Pollard (No, 32) shows in his 

 figure 34. Between the opposing and adhering surfaces of the vomer 

 and maxillary there is a thin layer of brittle tissue that stains like 

 cartilage in weak aqueous solutions of safranin. It is not shown as 

 cartilage in Pollard's section of this region, and is apparently a fibrous 

 cartilage that is developed in the tissues that connect the two bones. 

 It is much more intimately related to the maxillary than to the vomer. 

 Thus, although these two bones can not be easily separated unbroken, 

 without boiling or maceration, there is such a definite plane of sepa- 

 ration between them that distinctly different origins seem to be in- 

 dicated. 



On the dorsal surface of the anterior end of the ectopterygoid, 

 and on the adjoining hind end of the palatal process of the maxillary, 

 the autopalatine rests, its hind edge lying almost exactly at the level 

 of the hind edge of the palatal process. On this process and on the 

 adjoining mesial surface of the tooth-bearing portion of the maxillary 

 there is a slight depression to receive the autopalatine, this depression 

 lying just anterior to pore 6 infraorbital, that is, just anterior to the 



