268 



fish (No. 5) the maxillary lies internal to the lachrymal, and its free 

 hind end is enveloped in dermal tissues that have their attachment 

 to the top of the coronoid process of the mandible. One cannot but 

 be struck by the resemblance to Polypterus. The supramaxillary furrow 

 of Scomber, lying internal to the lachrymal, is greatly changed, if not 

 in part aborted, but both it and the maxillary labial fold are found. 

 A perfectly normal mandibular labial fold is also found, and is attached 

 posteriorly to the free hind end of the maxillary, just as the corre- 

 sponding fold of Polypterus is attached to the labial. The preraaxillary, 

 in Scomber, extends backward nearly to the hind end of the maxillary, 

 as it is well known that it does in many Teleosts. 



In Amia the maxillary fold differs from that of Polypterus in that 

 it is not the oral edge of the fold that is continuous with that deeper 

 part of the upper lip from which the fold has been separated by the 

 cutting into it of the supramaxillary furrow. In the adult Amia this 

 connection is at about the middle of the internal surface of the fold, 

 while in embryos it is at its dorsal edge, the supramaxillary furrow 

 pinching off a part of the lip, instead of cutting into it. This difference 

 I do not, however, think is of morphological importance in this con- 

 nection. At the hind end of the supramaxillary furrow of Amia there 

 is a relatively deep recess which runs inward and backward between 

 the anterior edge of the coronoid process of the mandible and the 

 underlying upper surface of the ectopterygoid, resembling, in this, 

 that part of the furrow of Polypterus that turns inward between the 

 adjoining edges of the labial and the ascending process of the splenial 

 and the postero - inferior surface of the lateral process of the ecto- 

 pterygoid. The mandibular fold of Amia ends on the outer surface 

 of the mandible before it reaches the hind end of the maxillary bone, 

 being in this less complete than the fold in either Polypterus or 

 Scomber. 



The labial of Polypterus is thus seen to closely resemble, in 

 general position, the hind end of the maxillary bone of Amia and of 

 certain Teleosts. But the maxillary bones of Amia and Teleosts are 

 certainly of purely dermal origin, unless it be, perhaps, their articulai* 

 heads, a supposition that Sagemehl (No. 37, p. 102) considered as 

 wholly unwarranted. The labial of Polypterus, if it be of cartilage, 

 cannot accordingly be the homologue of the maxillary bone of Teleosts. 

 It may, however, represent part of an underlying cartilage in relation 

 to which the maxillary bones are developed, a supposition that will 

 be later again referred to. 



Polypterus thus apparently having a maxillary labial fold without 



