Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 6 1 



The inner surface of the piece is usually slightly concave, and faces 

 backward and slightly downward. The outer surface is slightly 

 convex, faces forward and upward, and has, along its median line, 

 a slight ridge. The inner surface, on each side, rests against, and 

 is firmly bound by fibrous tissues to, the outer surface of the ante- 

 rior end of the maxillary, that bone extending from the upper to 

 the lower edge of the body of the piece. The outer surface of the 

 piece, on either side, rests against, and is firmly bound by tissue to, 

 the inner surface of the ascending process of the premaxillary, the 

 ventral part of the anterior edge of the latter bone resting against 

 the ventral, median shank of the rostrale. The median ridge on 

 the outer surface of the rostrale, which extends also onto the shank 

 of the piece, lies between the adjoining, antero-mesial edges of the 

 premaxillary bones, but it does not come to the level of their outer 

 surfaces, lying everywhere internal to their outer edges, and being 

 covered by the fibrous or ligamentous tissues that bind the two 

 premaxillaries together. The median groove on the inner surface 

 of the rostrale rests upon, and articulates with, the median, ante- 

 rior, ante-ethmoidal process or beak of the chondrocranium and 

 skull. 



The Maxillary (MX) is a long, flat, doubly-curved bone, the 

 hollow of one curve directed inward, that of the other downward 

 and forward. The anterior end of the bone is enlarged and 

 thickened, and has its anterior border bevelled to a narrow 

 edge. Dorsal to this bevelled edge, on the dorsal edge of the bone, 

 there is a strong articular head directed upward and mesially ; and 

 ventral to the bevelled edge there is, on the outer surface of the 

 bone, a small, flat, oval, articular surface directed forward and 

 laterally. The middle and most anterior portion of the bevelled 

 edge projects slightly, and there is, on each side of it, a small artic- 

 ular surface. Immediately dorso-posterior to the ventral articular 

 surface there is, on the ventral portion of the outer surface of the 

 bone, a small but strong process directed laterally and forward, 

 and having on its anterior surface a small, well-formed, articular 

 eminence. Immediately postero-dorsal to this process there is 

 still another articular surface which occupies a shallow depression 

 in the outer surface of the bone. Each of these several articular 

 surfaces is covered with a thin laver of tissue that adheres 



