MOEPHOLOGY OF TELKOSTEAN HEAD SKELETON. 539 



in that it gives a long continuous surface of attachment to the 

 ethmoid cartilage (e.) from the parethmoid cornu (e. ji. c.) 

 to the pre-ethmoid cornu (e. iir.). 



Walther (83, pi. 1, figs. \, 7) gives two figures of the 

 Pike's chondrocranium at two very early stages. In the one 

 the ethmoid is very short, and the expanded extremity of 

 the palatine process bears to it apparently the same relation- 

 ship as that jnst described for Amia. In the other, which 

 was older, the ethmoid is of considerable length, and exhibits 

 well-marked pre-ethmoid and parethmoid cornua; with each 

 of these the palatine process is connected, but not with the 

 intervening portion of the ethmoid. The anterior connection 

 is by far the stronger, whilst the hinder is so weak as to 

 suggest that it is secondary. Whether this is so, or whether 

 the two are formed by a breaking into two of the single 

 connection by fenestration, it is impossible to decide; the 

 fact remains that at this early stage two such connections 

 exist. 



In the stickleback the attachment is solely to the 

 pre-ethmoid cornu (fig. 7, e. l'>r.). The same is true for 

 Syngnathus and Siphonostoma (fig. 48, qu. fa.), for the 

 ethmopalatine {j)a.) must nndoubtedly be regarded as the 

 homologue of the palatine process. 



Thus in the development of these four distinct types of 

 fishes there are three different modes of attachment between 

 the palatine process and ethmoid, which by reason of their 

 early appearance in ontogeny seem to exhibit something of a 

 fundamental nature {v. 2^P-)- 



Meckel's cartilage has now a recognisable coronoid and 

 angular processes, with an articular facet between, and as a 

 whole it is little more than one third the length of the hyo- 

 mandibulo-symplectic tract. That of the trout (Winslow, 

 98) is nearly twice the length of this. The shortness of the 

 palatine process, combined with the equally short mandible, 

 gives to the stickleback its characteristically small gape. 



Thus all the peculiarities in the development of the 

 ethmoid, and of the hyoid and mandibular arches, which 



