MUSCULAR SYSTEM 143 



1. Constrictor arcuum visceralium, incl. constrictor superficialis 



dorsalis and ventralis. 



Innervation, 



Levator labii superioris ^ 



, , maxillae , , 

 ,, palpebrse nictitantis l ) 



rostri 



,, hyomandibularis y VII. 



Depressor rostri 



,, mandibularis and hyomandibularis, 



Interbranchiales IJt 



Trapezius 



risj 



2. Arcuales dorsales IX, X. 



3. Adduetores, incl. adductor mandibulaj .... V. 



and adductores arcuum branchialiuni. . . IX, X. 



B. Spinal muscles (originally longitudinal), divided, like the 

 trunk-muscles, into myotomes. Supplied by the spino- 

 occipital ( = the " ventral roots" of X) and spinal 

 nerves. 



(a) Epibranchial spinal muscles, dorsal to visceral skeleton. 



Innervation. 



4. Subspinalis . ... Spino-occipital nerves. 



( Spino-occipital nerves, 



5. Interbasales. . . < as well as the first 



( spinal nerve. 



(6) Hypobranchial spinal muscles, ventral to visceral skeleton. 



r Spinal nerves, and 



6. Coraco-arcuales, iucl. coraco-bran- I part ly the last one or 



chiales, coraco-hyoideus, and < more of the spino . 

 coraco-mandibularis . . { occipital nerves. 



The structure of the cranio-visceral musculature of Ganoids and Teleosts 

 differs considerably from that roughly sketched out above, so that the 

 different groups of muscles must be arranged in an entirely different manner. 

 Thus in Teleostei the following divisions may be distinguished : (1) Muscles 

 of the jaw, (2) muscles of the dorsal, and (3) muscles of the ventral ends of 

 the visceral arches. Each of these groups may again be sub-divided, but 

 further details about their arrangement, which is often very complicated, 

 cannot be given here. The visceral muscles of Polypterus are of especial 

 interest, as they show an intermediate condition between those of Elasmo- 

 branchs and Urodeles. 



Amphibia. It is to be expected, a priori, that the muscula- 

 ture of the visceral skeleton should be more highly developed in 

 branchiate than in air-breathing Amphibians ; we thus find 

 that in the former more primitive relations are met with, connect- 



1 This muscle has therefore nothing to do with the ether eye-muscles. 



