(^(^ ALUS. [Vol. XVIII. 



process may, therefore, lepresent the separate septomaxillary of 

 Amia, and certain lines in the bone, in Scomber, seem to indicate, 

 slightly, that there was here a separate center of ossification. The 

 ossification in Scomber, however, does not begin, externally, on the 

 ventro-lateral edge of the skull and ossify inward, as the bone in 

 Amia does, which may indicate that while there is homology in the 

 region there is none in the bones (No. 7). It may be noted that 

 Sagemehl considers the articulation of the septomaxillary with the 

 maxillary as the primary arrangement in fishes, the articulation 

 with the palatine being a secondary one. 



The Preorbital Ossification (PRE) is an irregular bone 

 having somewhat the appearance of an X applied to the outer 

 surface of a part of a sphere. The arms of the X are raised con- 

 siderably above the body of the bone, and their outer surface is 

 marked with sculptured lines, which run from the end of the 

 dorso-posterior arm downward and forward to the end of the 

 ventro-anterior one, and from each of the four arms into the two 

 adjacent ones. The two dorsal arms are somewhat fused with 

 each other; the two ventral ones are distinctly separate. The 

 ventro-posterior arm projects laterally as a strong, flat process, 

 and its ventral edge, which forms the arc of a circle and is capped 

 with cartilage, forms the posterior of the two articular surfaces 

 by which the palato-quadrate articulates with the cranium. In 

 Salmo the homologue of this process is said by Parker to form 

 the anterior articulation of the palato-quadrate with the cranium, 

 and it is called by him the anterior facial connective growth. The 

 still more anterior, ethmoidal, or septomaxillary articulation, of 

 Scomber, is, according to Parker's descriptions, replaced in Salmo 

 by an articulation with the maxillary (No. 50, p. 109), but this 

 does not seem to agree with his Fig. 2, Plate VI. 



The ventro-anterior arm of the X of the preorbital ossification 

 is connected by suture with a lateral process of the vomer that 

 arises from that bone near its anterior end. The dorso-posterior 

 arm extends backward under the frontal, and there forms part of 

 the roof of the orbit. The posterior portion of this part of the 

 bone is flat, thin, and relatively broad, and lies directly against the 

 under surface of the frontal without the intervention of a layer 

 of cartilage. The rest of the dorsal surface of the bone, except- 



