ANATOMY OF VERTEBRATES. 119 



and immovably articulated with the prenasal and maxillary bones, 

 in both the Sword-fish and the Garpike. The premaxillaries are 

 commonly more extended in the transverse than in the vertical 

 direction ; but there are many examples in Fishes where their de- 

 velopement is equal in both directions. The vertical extension, 

 which forms the nasal branch of the premaxillary, is of unusual 

 length in the fishes with protractile snouts, as, for example, in the 

 Picarels (Meniclce), the Dories (Zeus), and in certain Wrasses, as 

 Coricus, and especially the Epibulus, or Sparus insidiator of 

 Pallas, fig. 87, 22. In this fish the nasal branch of the inter- 

 maxillary, ib. 22', 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 descend- 

 ing or maxillary branch is attached 

 by a ligament, ib. 22 ", longer than 

 itself, to the lower end of the maxil- 

 lary bone, ib. 21, and consequently 

 draws forward that bone, together with 



the lower jaw, tO which the Same end Mechanism of protraction and retraction 

 „. >n • tit t oi the mouth (Epibulus insidiator) 



of the maxillary is attached by liga- 

 ment, when the long nasal branch of the premaxillary glides 

 forward out of the epicranial groove. The protractile action is 

 further favoured by a peculiar modification of the hypotympanic, 

 ib. 28, which, by its great length and movable articulation at 

 both ends, cooperates with the long premaxillary in the sudden 

 projection of the mouth, by which this fish seizes the small, agile, 

 aquatic insects that constitute its prey. In the Lopliius the nasal 

 processes of the premaxillaries enter a groove in the frontal: 

 in the Uranoscopus they also reach the frontal, playing upon the 

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

 vomer. In the Dactylopterus they penetrate between the nasal 

 and the vomer, and play in the cavity of the rhinencephalic arch. 

 The diverging appendage of the palato-maxillary arch consists, 

 in Fishes, of the pterygoid and entopterygoid bones, which, as 

 they are the least important parts of the arch, so are they the 

 least constant : they are wanting, for example, in the Synodon, 

 Platystacus, Hydrocyon, and Lopliius ; are connate with, or 

 indistinguishable from, the palatine in most Salmonoids and Eels ; 

 whilst in the Murama a single bone, the pterygoid, exists, but is 

 disconnected with the maxillary arch. Most Fishes, however, 

 present, as in the Cod, the two bones above named. The ento- 

 pterygoid is edentulous in the Perch, fig. 84, 23, Cod, and most 



