90 FISHES. 



(26), connected by means of the metapterygoid (27) with the 

 edo- (24) and ento-pterygoid (25), the foremost bone of the 

 arch being the palatine (22). All these bones have been 

 sufficiently described above (p. 55), and it remains only to be 

 mentioned that the bones of the palatine arch are but rarely 

 absent, as for instance in MurceTwphis ; and that the sym- 

 plectic does not extend to the articulary of the mandible, as 

 in Amia and Zepidosteus, though its suspensory relation to the 

 Meckelian cartilage is still indicated by a ligament which 

 connects the two pieces. Of the mandibulary bones the 

 articulary (35) is distinctly part of Meckel's cartilage. Fre- 

 quently another portion of cartilage below the articulary 

 remains persistent, or is replaced by a separate membrane- 

 bone, the angular. 



4. Memhrane-hones of the alimentary portion of the visceral 

 skeleton of the skull. — The suspensorium has one tegumentary 

 bone attached to it, viz. the prmoperculum (30) ; it is but 

 rarely absent, for instance in Murcenophis. The premaxil- 

 lary -iyi) and maxillary (18) of the Teleostei appear to be 

 also membrane -bones, although they are clearly analogous 

 to the upper labial cartilages of the Sharks. The pre- 

 maxillaries sometimes coalesce into a single piece (as in 

 Diodon, Mormyrus), or they are firmly united with the 

 maxiUaries (as in all Gymnodonts, Serrasalmo, etc.) The 

 relative position and connection of these two bones differ^ 

 much, and is a valuable character in the discrimination of 

 the various families. In some, the front margin of the jaw is 

 formed by the premaxiUary only, the two bones having a 

 parallel position, as it has been described in the Perch (p. 

 53) ; in others, the premaxiUary is shortened, allowing the 

 maxillary to enter, and to complete, the margin of the upper 

 jaw ; and finally, in many no part of the maxillary is situated 

 behind the premaxiUary, but the entire bone is attached to 

 the end of the premaxiUary, forming its continuation. In 



