THE NECTURUS 37 



The origin and insertion are easily seen. What is the 

 action ? 



Cut across the geniohyoids and deflect the ceratohyoids 

 to show the other ventral muscles. 



Ceratohyoid internus 



This small fusiform muscle is beneath the anterior end 

 sf the ceratohyoid externus. It is one of the hyoid series. 



Sternohyoid 



Ventral to the geniohyoids and also joined in the median 

 line are the sternohyoids. They are large, flat muscles that 

 help in the formation of the musculature of the body. The 

 insertion is seen to best advantage from the inner or dorsal 

 side of the visceral apparatus. Note that a small slip of 

 this muscle is attached to the shoulder girdle between the 

 procoraco-humeralis and the supracoraooideus. Turning 

 back to the head again, note the large muscles of the back 

 that are attached to the posterior end of the skull. These 

 muscles are not much specialized in the Urodeles. 



Levators 



On the back of the neck in the area marked off by the 

 masseter and ceratohyoid, are two small muscles that are 

 connected with the elevating of the gills. The anterior 

 is the levator arcuum branchiarum and the posterior is the 

 levator branchiarum. 



The levator arcuum branchiarum originates on the skull 

 and is inserted on the superior angle of the branchial 

 cartilage. 



The levator branchiarum, the second of the levators is 

 inserted at the base of the gills. It is fan shaped, lighter, 

 and more delicate than the other. 



