No. 2.] AMIA AND TELEOSTS. ^t'] 



The second and third intermuscular septa have their central 

 attachments on the occipital part of the skull, the large 

 occipito-superclavicular ligament lying in the third septum, 

 with its outer end in the horizontal line of the outer ends of 

 the horizontal ribs. 



The line of attachment of the first septum traverses the 

 hind end of the posterior process of the intercalar, and the 

 pedicle and three other processes of the suprascapular are en- 

 veloped in, or lie in definite relations to, different parts of it. 



The anterior muscle-segments, on each side of the head, 

 extend forward on the dorsal surface of the skull in two deep 

 grooves, the lateral one of which corresponds closely in position 

 to the temporal groove of Amia. This groove lies, however, in 

 Scomber, on the dorsal surface of the parietal and frontal 

 bones instead of, as in Amia, between those bones and the 

 chondrocranium. The anterior margin of the muscle-segments 

 in Scomber extends forward slightly beyond the posterior por- 

 tion of the supraorbital lateral canal, covering externally that 

 canal, while in Amia it only reaches, approximately, the hind 

 edge of the frontal bone. The temporal extensions of the 

 trunk muscles, which are certainly secondary adaptations, thus 

 extend considerably farther forward in Scomber than they do 

 in Amia. 



In Amia the first intermuscular septum has the same general 

 relations to the intercalar and to the pedicle of the supra- 

 scapular that the first septum in Scomber has. The fourth 

 and fifth septa have their central attachments to the two 

 occipital arches, and each usually contains one of the two 

 occipito-supraclavicular ligaments of the fish. In one larval 

 fish these two ligaments were found in the third and fourth 

 septa. 



In Scomber the dorsal and ventral roots of the nerves of 

 the fifth and sixth trunk-segments both traverse foramina that 

 perforate, respectively, the first and second free vertebrae of 

 the fish, the foramina in each vertebra lying posterior to the 

 intermuscular septum that has its attachment to the vertebra. 

 Both nerves have dorsal, ventral, and horizontal branches, and 

 from each nerve a communicating branch is sent dorsally, but 



