267 



to the anterior end of the larger fold, and ends posteriorly at the 

 antero-inferior corner of the labial, to which it is attached. 



The so-called labial, or labial cartilage, of Polypterus is, in 30-cm 

 specimens, a somewhat flexible piece, and looks much more like tough 

 gristle than it does like true cartilage. I have, however, made no 

 histological examination whatever of it. It is somewhat triangular in 

 shape, its postero- dorsal edge being the longest one of the three. 

 That edge is straight, the other two being somewhat rounded, and 

 separated by a rounded angle. The piece lies against the lateral 

 surface of the ascending process of the splenial, its dorsal corner lying 

 against, or slightly below, the anterior corner of the dorsal edge of 

 the process. Its ventral edge is nearly horizontal in position, when 

 the mouth is closed, and lies, approximately, at the level of the base 

 of the process of the splenial, the ventro-posterior corner of the carti- 

 lage lying in a slight groove found immediately internal to the dorsal 

 edge of the dermarticular. 



The labial is enveloped in a thin layer of the tissues that form 

 the lips of the fish, and its superior corner is strongly attached, by 

 those tissues, to the antero-dorsal corner of the ascending process of 

 the splenial, around which point as a pivot the labial is capable of a 

 certain amount of movement. The dorso-posterior edge of the piece, 

 enclosed in its dermal covering, is free. The anterior edge is loosely 

 attached, its full length, by the enveloping tissues, to the anterior 

 edge of the ascending process of the splenial, the sheet of tissue here 

 concerned being the hind end of that part of the lower lip of the fish 

 that lies against the mandibular teeth, internal to the mandibular la- 

 bial fold. A somewhat wide and glistening surface is thus here formed, 

 which abuts against and slides upon the similarly covered postero- 

 inferior surface of the lateral process of the ectopterygoid, that process, 

 as already stated, resting against and being strongly bound to the hind 

 end of the tooth-bearing part of the maxillary. The sheet of tissue 

 that covers this process of the ectopterygoid is the hind end of that 

 part of the upper lip of the fish that lies against the maxillary teeth, 

 internal to the maxillary labial fold. The ventral edge of the labial 

 gives attachment to the hind ends of both the maxillary and mandi- 

 bular labial folds, as already stated. 



The labial, excepting only its ventral margin, lies, when the mouth 

 is closed, internal to bone Y" of Traquair's descriptions, and internal 

 also to the postorbital portion of the maxillary bone. In this it differs 

 from the hind end of the maxillary bone of Amia, but strikingly re- 

 sembles the hind end of the maxillary bone of Scomber. In the latter 



