162 University of (Udifovnia Puhlications in Zoology [Vol. is 



except for a slight decrease anteriorly. They are inserted ventrally 

 on the anterior part of the copula of the hyoid arch. A few of the 

 more lateral fibers are inserted by tendinous tissue, in the tissue 

 joining the copula and ceratohyoid. 



4. Coracohranchiales (c. &r.^ ', fig. 4). The coracobranchiales are 

 the most internal or dorsal of the ventral longitudinal muscles. They 

 include seven pairs which form an almost solid wall along the sides 

 of the pericardial cavity. The first has its origin in the connective 

 tissue directly over and attached to the coracohyoideus muscles. The 

 origins of the second to the sixth coracobranchiales are in the strong 

 connective tissue just dorsal to the coracoarcuales. The anterior part 

 of tlie origin of the seventh is continuous with the origin of the sixth, 

 while the posterior part has its origin on the pectoral girdle, just 

 laterad of the origin of the coracoarcuales. It extends along about 

 one-fourth of the ventral part of the pectoral girdle. Near their 

 origin these muscles form an almost continuous sheet, but they are 

 separated toward their insertions by the afferent arteries. The first 

 to the fifth are also divided from their origin about two-thirds of 

 the way to their insertions by the anterior parts of the ventral inter- 

 branchial muscles. The sixth and seventh coracobranchiales are 

 separated by the sixth interbranchial. 



The first coracobranchialis passes anteriorly and dorsally and is 

 inserted on the posterior edge of the basihyoid. The second to the 

 sixth are inserted posteriorly on the hypobranchial segments of the 

 corresponding branchial arches, while the greater part of the seventh 

 is inserted on the ceratobranchial of the last gill-arch. The insertion 

 of the seventh extends ventrally throughout the entire length of the 

 segment. The most anterior fibers, however, are inserted on the ante- 

 rior edge of the posterior median piece. The hypobranchial segment 

 of the seventh arch is absent or fused with the basal piece. 



Musculature Associated With the Organs op Special Sense 

 In this division are located the muscles of the eye and of the organ 

 located in the parietal fossa. The eyelids of Heptanchus are mem- 

 branous and consequently musculature is not developed in them. 



I. Eye-muscles (fig. 5). The six muscles of the eye-socket are 

 divided into two groups. The first or oblique group is placed ante- 

 riorly and consists of two muscles, the superior {s.o.) and inferior 

 oblique {i.o.). These two muscles extend from the anterior part 

 of the orbit outward and backward and are inserted on the eyeball. 



