390 H. B. POLLARD, 



Behind the intermaxillaris posterior is a separate muscle which 

 arises from a median raphe of its o^Yn, and proceed to the postero- 

 internal angle of the jugular plate. Some fibres pass on into the 

 mantle. 



The innervation of the intermaxillaris posterior and of the muscle 

 to the jugular plate is from the Ramus hyoideus of the Facial. 



The action of these muscles is chiefly to aid in swallowing and 

 to bring together the jugular plates. 



Interarcuales ventrales (fig. 6). 



The first of these takes its origin from the lower third of the 1st 

 ceratobranchial. It proceeds downwards, inwards and forwards and 

 attaches itself by a short tendon to the lower end of the ceratohyal. 

 Its innervation is from the post trematic branch of the Glossopha- 

 ryngeus. 



The second arises from a tubercle, near the lower end of the 

 second ceratobranchial. Some fibres pass to the interbranchial mem- 

 brane but the main portion passes under the tendon of coracoarcualis 2 

 and then becomes somewhat broader and flatter. Its attachment is 

 to the ceratohyal by a short tendon near that of the first. 



The common 3rd and 4th interarcuales pass from the respective 

 ceratobranchials beneath the body of coracoarcualis 2 and are attached 

 to the 2nd (cartilaginous) basibranchial. The innervation of the last 

 2 muscles was not observed but is no doubt from the corresponding 

 posttrematic branch. 



Levatores arcuum. 



These muscles take their origin together from the under portion 

 of the ridge on the backward process of the petrosum. The Levator 

 arcus primi passes down, just above the forking of the two pharyngo- 

 branchials to the top of the 1st ceratobranchial. It is innervated by the 

 posttrematic branch of the Glossopharyngeus. 



The remaining levatores pass downwards and backwards together 

 to the tops of the ceratobranchials of the respective arches. Beyond 

 the last ceratobranchial a muscular slip continues on and is inserted 

 into the skin ligaments in front of the shouldergirdle. Innervation is 

 from the posttrematic branches of the Vagus. 



No adductores arcuum (Vktter) are present. The epibranchials 

 are either not present or fused with the ceratobranchials. 



