BONES OF THE HEAD OF FISHES. 5 



the anterior angle of the orbital cavity to its posterior angle, and 

 thus completes the circle of the orbit. Further, inwards is 

 seen also on each side a kind of vertical partition, (Fig. 247 $,) 

 which is suspended to the skull, and which separates the orbits 

 and the cheeks from the mouth. It is formed by bones cor- 

 responding with the palatine, pteregoid, and tympanic bones of 



FIG. 248. Bones of the head of the Perch, after the removal of the jaws, lateral par- 

 tition, and operculum, on one side, to show the interior of the mouth, and the hyoid 

 apparatus; c, cranium; or, orbit; v, vomer (armed with teeth); im, superior maxil- 

 lary ; dp, teeth implanted on the palatine arch ; mi, lower jaw ; I, lingual bone ; 6, 

 lateral branches of the hyoid apparatus ; *, process for the attachment of these to the 

 lateral partition ; r, r, branchio-stegal rays ; a, branchial arches : ph, superior pharyn- 

 geal bones ; ar, articular surface by which the lateral partition is attached ; o to h, bony 

 framework supporting the pectoral 6n,p / o and o', scapula divided into two pieces ; h, 

 humerus ; ab, bone of the fore-arm ; ca, bone of the carpus ; co, coracoid bone. 



the higher Vertebrata. At its under part it gives attachment to 

 the lower jaw ; and behind it is prolonged in such a manner, as 

 to form a kind of moveable flap, which protects the respiratory 

 apparatus, and is termed the operculum or gill-cover. The 

 lower-jaw is formed of three pieces on each side. Within the 

 lateral partitions just described, and lying at the bottom of the 

 mouth, is found a framework of very complicated structure, 



