HEAD AND NECK. 107 



fall into three groups. 1. Interarcual muscles. 2. 

 Adductors, serially homologous with the great mandibular 

 adductor. 3. Ventral longitudinal muscles, these arise from 

 the coracoid bar as a common mass and are inserted in pairs 

 into the base of each visceral arch. 



Vetter, Jena. Zeitschr., Bd. viii. 1873-74, p. 405. 



C. 85. Head of a Haddock (Gadus ceylejinus), showing the super- 

 ficial muscles of the left side. In this and other bony fish 

 the muscles of the head are far more numerous and subdivided 

 than in the Dog-fish, although their phylogenetic origin 

 from similar simple muscle-sheets can be inferred with some 

 degree of certainty. The specialization of the muscles is 

 closely related to the greater number of skeletal parts and 

 their increased mobility ; it is particularly apparent in the 

 adductor of the jaw and in the opercular muscles. In all 

 probability the opercular palatine and hyoid muscles 

 represent the great superficial constrictor of the Selachian. 

 Vetter, Jena. Zeitschr., Bd. xii. 1877-78, p. 489. 



C. 86. The muscles of the left branchial arches of a Haddock 

 (Gadus ceglefinus). The muscles are highly specialized and 

 provide for a great variety of movement, both of the 

 individual arches and o the branchial skeleton as a whole. 

 The dorsal muscles in particular, owing no doubt to their 

 connection with the pharyngeal toothed pad formed by the 

 hypopharyngeal bones, show a high degree of complexity 

 and can produce movements in anterior, posterior, dorsal 

 and lateral directions. 



C. 87. Head of a Python (Python sebci), showing the chief 

 muscles. They fall into three groups. 1. Those concerned 

 in the movements of the lower jaw, consisting of parieto- 

 quadrato-mandibularis, analogous in function to the temporal 

 and masseter of mammals ; occipito-quadrato-mandibularis, 

 analogous to the depressor maxillae inferioris (digastric); 

 transverso-maxillo-pterygoideo-mandibularis, analogous to 

 the external pterygoid; and a curious pair of muscles 

 (intermaxillares) that pass diagonally across the floor of the 

 mouth from either mandibular joint to the anterior end of the 



