108 



LECTURE V. 



the intermaxillary (^ib. 



S7 





Mechanism of protraction and retrac- 

 tion or tlie mouth (Epibulus insidi- 

 ator). 



plays in a groove on the upper surface 

 of the skull, and reaches as far back as 

 the occiput when the mouth is retracted. 

 The descending or maxillary branch is 

 attached by a ligament {ib. 22"), longer 

 than itself, to the lower end of the max- 

 illary bone {ib. 21.), and consequently 

 draws forwards that bone, together with 

 the lower jaw, to which the same end of 

 the maxillary is attached by ligament, 

 when the long nasal branch of the pre- 

 maxillary glides forwards out of the epi- 

 cranial groove in which it usually lies. 

 The protractile action is further favoured by a peculiar modifica- 

 tion of the hypo-tympanic {ib. 28), which, by its great length and 

 movable articulation at both ends, co-operates with the long pre- 

 maxillary in the sudden projection of the mouth, by which this 

 fish seizes the small, agile, aquatic insects that constitute its prey. 

 In the Lophius the nasal processes of the premaxillaries enter a 

 groove in the frontal : in the XJranoscopus they also reach the frontal, 

 playing upon the small nasal bone and pressing it down, as it were, 

 upon the vomer. In the Dacfylopterus they penetrate between the 

 nasal and the vomer, and play in the cavity of the rhinencephalic 

 arch. 



The small bony piece situated above the maxillary in some Ilale- 

 coids (Trout, Herring) and Lucioids (Pike) seems to belong to the 

 series of mucous or scale bones : the Flying Gurnard {Dacty- 

 lopterxis) has two delicate cartilages in a similar position, and the 

 ScicE7ia aquila a large labial cartilage in the angle of the mouth, 

 attached to the lower jaw. 



The Diverging Appendage of the pa lato -maxillary arch consists, in 

 Fishes, of the pterygoid and entopteiygoid bones, which, as they are 

 the least important parts of tlie arcli, so arc they the least constant : 

 they are wanting, for example, in the Synodon, Platystacus, Ilydro- 

 cyon, and Lophius ; ai'e connate with, or indistinguishable from, the 

 palatine in most Salmonoids and Eels ; wliilst in the Murfsna a single 

 bone, the j^terygoid, exists, but is disconnected with the maxillary 

 arch. Most Fislies, however, present, as in tlie Cod, the two bones 

 above named. 



The ento-pterygoid {fig. 30. 23) is an oblong, thin, scale-like bone, 

 attached to the inner border of the co-adnpted halves of the palatine 

 and true pterygoid, and increasing the bony roof of the moutli in 



