164 ALUS. [Vol. XVIII. 



gives insertion to a tendon of the ventral one of the two adductor 

 profundus muscles. Both of these eminences are often so strongly 

 developed that they form the true end of the ray. On the mesial 

 half-ray, at or slightly distal to the base of its proximal process, 

 there is a second eminence. On the first five rays, approximately, 

 it gives insertion to a tendon of the dorsal one of the two adductor 

 profundus muscles, while on the remaining rays it gives insertion 

 to a tendon of the adductor superficialis muscle. The rays are 

 bound by strong fibrous tissues to the primary girdle, in such a 

 manner that a somewhat limited movement is permitted them in 

 the plane of the girdle, and a much more extended movement at 

 right angles to that plane. 



Lateral Line System. 



The lateral line system of Scomber differs from that of Amia 

 in that there are, apparently, fewer lines of surface pit organs, and 

 that there is no connection whatever between the canals of the two 

 sides of the head. The pit lines that are apparently wanting, as 

 compared with Amia, are those found on the cheek, mandible and 

 gular plate of the latter fish. The antorbital commissural canal, 

 formed, in Amia, by a large and important anterior continuation 

 of the infraorbital canal of each side of the head, and found in 

 certain other fishes, in whole or in part, as a line of surface pit 

 organs, has apparently been developed, in Scomber, as a short 

 canal, on each side of the head, fused with and forming the an- 

 terior end of the supraorbital canal. The posterior, supratemporal 

 cross-commissure of Amia is represented on each side of the head 

 of Scomber by a canal which does not meet its fellow of the op- 

 posite side in the middle line of the head. Otherwise there are no 

 important diff'erences in the course and disposition of the main 

 canals. The branch canals, or dendritic systems, on the contrary, 

 differ greatly, in that they undergo much less frequent subdivision 

 than in Amia, and that the subdivisions are in many cases carried 

 so deep that the trunk of the system disappears, leaving the 

 branches as separate tubes arising directly and independently from 

 the main canal. Similar subdivisions were found, in Amia, only 



