IV 



MUSCULATURE 



MUSCULATURE OF HEPTANCHUS I\rACULATUS 



The muscles in Hepianchus may be divided into two groups. In one the fibers 

 are short, reaching from one connective tissue septum (myoseptum) to an- 

 other; in the other thej' are more 

 or less extended and are not con- 

 fined within myosepta. The mus- 

 cles of the body are of the short 

 type; while those of the eyeball, 

 of the hypobranchial region, and 

 of the claspers in the male are of 

 the long type. 



In a side A^ew the muscles of the 

 body of Hepfanchus maculatus 

 are divided at the lateral line {II., 

 fig. 90) into dorsal bundles (f?.6.) 

 which attach to the cranium, and 

 ventrolateral bundles which at- 

 tach to the i)ectoral girdle. Both 

 the dorsal and the ventrolateral 

 muscles extend to the tip of the 

 tail. In these bundles the myo- 

 septa {)ns.) are bent into zigzag 

 shape. Above the lateral line one 

 of the columns has the apices of 

 its myosepta directed forward, 

 the other backward. Below the 

 line there appears to be a single 

 column with apex pointed pos- 

 teriorly. Some of the anterior 



fibers of the ventral bundle are specialized as the pectoral muscles of the 

 pectoral fin. Of the long muscles we may consider those of the eyeball first. 



Muscles of the Eye 



Two groups of muscles are present in the orbit. The first group is placed an- 

 teriorly and consists of the superior oblique {s.o., fig. 91) and inferior oblique 

 [i.o.) muscles. These muscles extend from the anterior part of the orbit out- 

 ward and backward to be inserted on the eyeball. The second group consists 



Fig. 90. Lateral view of body musculature in 

 pectoral region, Heptanchtts maculatus. (Evelyn 

 Forsytlie, orig.) 



cl., gill cleft; d.l)., dorsal bundle; d.f., dermal 

 fin-rays; d.r.m., dorsal radial muscles of pectoral 

 fin ; /.&., lateral bundle ; II., lateral line ; ms., myo- 

 septum; tr., trapezius muscle; v.h., ventral me- 

 dian muscle. 



[89] 



