— 23 — 



being replaced hy menibrane, which mciubranc might easily be invaded by outgrowths from a neigh- 

 bouring membrane bone. 



In Gonorhynchus Greyi there is, according to Ridewood ('05 b), a process that would seera to 

 be similar to that of Gasterostcus and Gottiis, but somewhat more developed, for it is said to come 

 into contact with the sphenotic (postfrontal, Ridewood) as well as with the alisphenoid. 



In Osteoglossum formosum, Bridge ('95) describes two processes on the parasphenoid, one of 

 which would seem to be exactly similar to that of Gonorhynchus; for, although its relations to the 

 trigeminus foramen are not given , it is said to come into contact with both the sphenotic and ali- 

 sphenoid. Bridge considers this process of Osteoglossum as the equivalent of the processes of Amia, 

 Acipenser and Polypterus; but if, as seems so evident, it is simply an exaggerated development of 

 the processes of Gasterosteus and Cottus, it can not be the equivalent of the process of Amia. It is 

 also not the homologue of the process of Polypterus, as is shown immediately below. Whether it is 

 the homologue of the process of Acipenser, or not, I can not determine from the descriptions and 

 figures that I find of that fish. 



The second process of the parasphenoid of Osteoglossum is said by Bridge to grow out of the 

 lateral edge of that bone immediately ventral to the root of the ascending process. It projects laterally 

 and slightly upward, and gives articulation to an articular surface on the dorsal edge of the metaptery- 

 goid. It is said to have no parallel in any other teleostean fish, but to be represented in Lepidosteus 

 by what is an essentially similar process. This process in Lepidosteus is fully described in the chapter 

 of this work devoted to the myodome, and that it is the homologue of the process of Osteoglossum 

 seems to me, from the figures of this latter fish, very doubtful. 



In Polypterus, according to Traquair ('70), the ascending process of the parasphenoid has not 

 only a horizontal portion, or process, which may perhaps be the homologue of the horizontal process 

 of Osteoglossum, but also two dorsal prolongations. One of these dorsal prolongations is apparently 

 the homologue of the sphenotic Prolongation of the process of Amia, the other being still a third 

 Prolongation, not described in any other fish, which projects dorso-posteriorly, embraces the facialis 

 foramen, and comes into contact with the so-called opisthotic bone. 



P R E M A X I L L A R Y. 



The preraaxillary consists of a curved body, offen called the horizontal part of the bone, and 

 three processes which rise perpendicularly to that body. The curved body of the bone ends in a blunt 

 point, and its oral surface is covered, nearly its füll length, with sniall villiform teeth, while on its 

 dorsal surface, and extending its füll length, there is a slight groove. The three processes of the bone 

 rise from the ental edge of this groove, and the groove lodges the ventral edge of the maxillary. 



One of the three processes of the premaxillary is a thin triangulär flange that rises, longitudin- 

 ally, from the distal half of the body of the bone. It projects upward and postero-mesially, per- 

 pendicularly to the body of the bone, lies against the internal surface of the maxillary, and, because 

 of this Position, may be called the postmaxillary process of the preraaxillary. In certain teleosts 

 this process forms the bind end of the premaxillary, the more distal portion of the bone of Scor- 

 paena being represented, in such fishes, by tough gristly connective tissue. This would seem to in- 

 dicate that the premaxillary primarily extended only to this process, and it would also seem to in- 



