86 ALUS. [Vol. II. 



In my work on Amia, already referred to, I fully described 

 all the occipital and first free spinal nerves in that fish, giving 

 at the same time their relations to the anterior muscle-segments 

 of the trunk, and the relations of these segments and their 

 myosepta to the bones of the skull, to the anterior vertebrae, 

 and to the bones of the shoulder girdle. Similar descriptions 

 of these nerves, and of the segments and bones they are related 

 to, form part of a work I have now nearly finished on Scomber 

 scomber. The dissections of this fish have been made under 

 my direction, in my laboratory here at Menton, by Dr. J. Dewitz, 

 and can be briefly summarized as follows : 



The sixth intermuscular septum is the first one that extends 

 from the mid-dorsal to the mid-ventral line of the body. The 

 ventral parts of the fifth and fourth septa, as seen on the inner 

 surface of the body wall, run downward, from the vertebral 

 column, on to the dorsal edge of a large accessory shoulder- 

 girdle bone, and there end. On the outer surface of the body 

 the fifth septum runs downward and forward to the hind edge 

 of the clavicle, at about the middle of its length, and there 

 ends. The fourth and more anterior septa run downward to 

 and end at the dorsal edge of the same bone. The sixth muscle- 

 segment, the one that lies immediately in front of the sixth 

 septum, is thus the first one that extends ventrally the full 

 length of the clavicle, and the fifth septum is the one that marks 

 the apparent septal position of the ventral end of the clavicle. 

 The fifth septum of Scomber is thus, in its relation to the clav- 

 icle, the apparent homologue of the same septum in Amia. 



Centrally the fifth septum is attached to the second free 

 vertebra of the fish, the fourth septum being attached to the 

 first vertebra. Articulating with each of these two vertebrae 

 there is, on each side, a single rib, which lies in the inter- 

 muscular septum attached to the vertebra, at the line where that 

 septum is intersected by the horizontal muscle-septum. On the 

 third and next following vertebrae there are, in addition to these 

 horizontal ribs, ventral ones, which lie along the inner surface 

 of the trunk muscles, in the mesial edges of the septa of the 

 vertebra to which they are related. In one specimen a short 

 rudimentary ventral rib was found on the second vertebra also. 



