MORPHOLOGY OF TELEOSTEAN HEAD SKELETON. 553 



pletely ossified there would be little to distinguish it from 

 that of Pagellus. 



The condition in the Cyprinodonts is a little difficult to 

 make out^ but is well seen in Characodon luitpoldi. By 

 careful examination of this, and by serial sections of this 

 region in a specimen of Haplochilus fasciatus, which Mr. 

 G. A. Boulenger kindly placed at my disposal, I am satisfied 

 that the condition in them differs from that in the pike only 

 in the shortness of the ethmoid, the more complete ossification 

 of parts, and in the absence of teeth on the palatine. 



The Acanthopterygii, with one or two notable exceptions, 

 conform to one or other of the conditions just described, or 

 are modifications of these. For example, in Pagellus ery- 

 thrinus the ethmoid is perfectly ossified, the parethmoid cornu 

 has practically disappeared, and the pre-ethmoid is greatly 

 reduced ; nevertheless the shape of the palatine and its 

 maxillary process, and the form of the ethmoid with its well- 

 marked rostrum, leave no doubt that it belongs to the same 

 type as that shown by its kindred species (fig. 45). Again, 

 inOdax Richardsoni the post-palatine articulation appears 

 to be formed by the pterygoid bones. 



It is no uncommon thing for the palatine to be strongly 

 attached to the vomer by ligament, and even to present a 

 flattened surface to that bone, e. g. Sciaena, but this is not a 

 feature of primary importance, nor does it affect the presence 

 of the other articulations. 



These facts prove that in Salmonidas, Esocidas, Cyprino- 

 dontidas, and Acanthopterygii (with exceptions to be dealt 

 with), one type of palato-ethmoidal relation exists, viz. one in 

 which the palatine process or its derivatives are attached to 

 the ethmoid at two points, the pre-ethmoid cornu and pareth- 

 moid cornu, by two facets, the pre-palatine and post-palatine. 



In the stickleback, during development, a post-palatine 

 attachment is always absent, a pre-palatine always present 

 (figs. 8, 9, e. 2>i'-) . The palatine bone itself is small, edentu- 

 lous, and possesses an insignificant maxillary process. The 

 ethmoid region is of the same type as that of the pike in 



