SKELETON. 59 



irregularly-sliaped epiiramhial (61). In the fourth arch the 

 hypobranchial is absent. The uppermost of these segments 

 (62), especially of the fourth arch, are dilated, and more or less 

 confluent ; they are beset with fine teeth, and generally dis- 

 tinguished as the upper pharyngeal lones. Only the cerato- 

 branchial is represented in the fifth arch or lower pharyngeal. 

 On their outer convex side the branchial segments are 

 grooved for the reception of large blood-vessels and nerves ; on 

 the inner side they support horny processes (63), called the 

 gill-raJcers, which do not form part of the skeleton. 



The scapular or humeral arch is suspended from the skull 

 by the (suprascapula) post-temporal (46), which, ia the Perch, 

 is attached by a triple prong to the occipital and mastoid bones. 

 Then follows the {scapula) supraclavicula (47), and the arch is 

 completed below by the union of the large (coracoid) clavi- 

 cula (48) with its fellow. Two flat bones (51, 52), each with 

 a vacuity, attached to the clavicle have been determined as 

 the (radius and ulna) coracoid and scapula of higher verte- 

 brates, and the two series of small bones (53) intervening 

 between the forearm and the fin as carpals and metacarpals. 

 A two-jointed appendage the (epicoracoid) posf-clavicula, is 

 attached to the clavicle : its upper piece (49) is broad and 

 lamelliform, its lower (50) styliform and poiated. 



The ventral fins are articulated to a pair of flat triangular 

 bones, the ^&ic bones (80). 



The bones of the skull of the fish have received so many 

 different interpretations that no two accounts agree in their 

 nomenclature, so that their study is a matter of considerable 

 difficulty to the beginner. The following synonymic table will 

 tend to overcome difficulties arising from this cause ; it contains 

 the terms used by Cuvier, those introduced by Owen, and finally 

 the nomenclature of Stannius, Huxley, and Parker. Those 

 adopted in the present work are printed in italics. The 



