552 H. H. SWINNERTON. 



tion with the pve-ethmoid cornu {2)a.'). The latter^ owing 

 to the formation of a rostrum^ such as was described for the 

 young salmon, is situated some distance behind the extremity 

 of the ethmoid; and, because of the ahnost complete ossifica- 

 tion of this, is bounded by the vomer below and nearly 

 surrounded by the mesethmoid above. Behind the palatine 

 bone the cartilage {qii. pa.) persists, and, as in the pike, it 

 offers a well-formed concave sm'face, which slides with 

 a lateral motion on the rounded, cartilaginous ventral surface 

 of the parethmoid. 



In Pagellus centrodontus (fig, 45) another modification 

 of the same type exists. Here, as before, the palatine (pa.) is 

 massive and dentigerous, but its maxillary process (pa. m.) 

 is much longer, more curved, more powerful. Bearing the 

 same relation to this as in Scomber is a facet for the 

 pre-palatine articulation. Here again, owing to the formation 

 of a rostrum even stronger than that of the Scomber, the 

 pre-ethmoid cornua are situated far back behind the end of 

 the ethmoid (e.), and lie mainly on the anterior portion of the 

 parethmoid bone, close to the suture between it and the vomer. 

 In this example, however, probably owing to the shortness of 

 the ethmoid, the post-palatine sliding surface is formed not 

 by cartilage, but by the hinder end of the palatine bone. 



As already pointed out, the larval salmon has both pre- 

 and post-palatine articulations. They are also present in the 

 adult Salmo trutta, but owing to the ethmoid being wholly 

 cartilaginous, the facets are not so conspicuous as in Scomber 

 and Pagellus. The pre-ethmoid cornu is much smaller, and 

 not so distinct as the other, but it nevertheless exists, and 

 was evidently seen,, though not noticed by Parker, for he 

 represents it in his figure of the ventral surface (pi. 7, 

 fig. 2) of Salmo salar at the posterior end of the '' curved 

 ridge." Thus the palato-ethmoid region in the salmon, on 

 the whole, conforms to that of the pike, and differs mainly in 

 the fact that elongation of the ethmoid takes place in the 

 latter between the cornua, and in the former in front of the 

 pre-ethmoid. If this region in the salmon were more com- 



