Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 221 



sharply forward. The angle formed at this latter point may be 

 called the dorso-posterior angle of the septum, the more dorsal 

 angle being called the dorso-anterior one. Ventral to its dorso- 

 posterior angle the septum curves gradually downward, and then 

 downward and backward, to the line of the outer ends of the hori- 

 zontal ribs, to one of which it is attached. \'"entral to this rib it 

 turns forward again, the septa between the anterior segments of 

 the trunk here presenting a sharp angle, which, between the pos- 

 trior segments examined, gradually becomes obtuse and rounded. 

 Curving downward, and then downw^ard and backward, the sep- 

 tum reaches a point lying approximately at the same distance ven- 

 tral to the horizontal rib that the apex of its dorso-posterior angle 

 lies dorsal to. There it turns sharply forward, forming an angle 

 that may be called the ventro-posterior one, the apex of this angle 

 lying directly ventral, or postero-ventral to that of the dorsal one. 

 Ventral to this ventro-posterior angle, the septum runs forward 

 and downward to the mid-ventral line of the body. 



From this zigzag surface line the septum extends inward into the 

 muscle mass, but, as in the adult Aniia, it is pulled or pushed for- 

 ward or backward, in several places, into more or less developed 

 'pocket-like portions. Of these pockets there are five in Scomber. 

 The most dorsal pocket can be called the dorso-anterior one. It is 

 a small pocket lying antero-internal to the dorso-anterior angle of 

 the zig-zag surface septal line, and is directed forward, approxi- 

 mately in the line of the middle line of the supratemporal groove 

 on the top of the skull. The second pocket can be called the dorso- 

 posterior one. It is larger than the dorso-anterior pocket, lies 

 postero-internal to the dorso-posterior angle of the surface septal 

 line, and is directed backward, approximately in the line of the 

 ridge of bone that separates the supratemporal and temporal 

 grooves. The third pocket is considerably larger than either of 

 the other two and can be called the dorso-median one. It is 

 directed forward, approximately in the line of the middle line of 

 the temporal groove, and occupies the entire space between the 

 dorso-posterior angle of the surface septal line and the angle that 

 marks the point where the septum is attached to the horizontal 

 rib. The fourth pocket is, in the middle part of the trunk, as 

 large as the third one, is directed forward, as that one is, and 



