MOEPHOLOdY OF CRAXIAL MUSCLES IN SO^fE VERTEBRATES. 203 



The interraandibularis, iu correlation with its development 

 in the mandibular segment, is usually innervated hy the Yth 

 cranial nerve. Vetter, however, found that in Scyllinm and 

 Prioiiodon the portion immediately behind the symphysis of 

 the jaws was innervated by the Vth, and the greater portion 



Text-fig. .30. 





3*"-^>a 



m^okij sub. 



of the muscle by the Vllth, and that in Acanthias, Heptan- 

 chus, and Scymnus the whole of the muscle was innervated 

 by the Vllth. He concluded that in the former the greater 

 part, and in the latter the whole, of the intermandibularis 

 (Csv^) had disappeared, and had been replaced by the inter- 

 hyoideus (Csv^), Avhich had gained a secondary insertion into 

 the lower jaw. But this opinion, which was founded on adult 



