MORPHOLOGY OP TK^MOSTEAN HMAD SKELETON. 581 



ill the number, shape, and proportional size of its pharyngo- 

 branchials, and in all other featui'es except the fusion of the 

 vestigial elements of the fifth arch. Again, the hyomandibu- 

 lar is of the same shape, though its articulations are more 

 generalised; the metapterj-goid is equally reduced; one 

 pterygoid line alone is present; the palatine is small, edentu- 

 lous, and lacks a maxillary process ; finally it presents the 

 acrartete condition. 



The similarity is so great that one may say with consider- 

 able truth that the little stickleback is but a slightly 

 specialised Belone. 



In the trunk region, however, though the pectorals are 

 raised, the pelvics, abdominal, and the ari-angement of the 

 other fins is the same as in Thoracostei ; j'et the complete 

 absence of bony plates and infra-clavicles gives some excuse 

 for not including the Scomberesoces in the new sub-order. 



Boulenger (01) has recently placed them as a family of the 

 Percesoces, and the possession of a reduced metapterygoid in 

 Atherina supports this view. It is interesting to note that, at 

 least so far as the head skeleton is concerned, they depart 

 from the other members of that sub-order in just those 

 features in which they approach the Gasterosteoidei ; for all 

 the other Percesoces I have examined possess a suspensory 

 pharyngeal, a well-developed opisthotic (Starks, 99), and the 

 acrartete condition. 



If this is their true position, it would strongly tend to 

 show that the acrartete condition was derived from a lowly 

 disartete by loss of the post-palatine articulation. If it is 

 not, then the most convenient way Avould be to keep the 

 Scomberesoces in a separate sub-order as before, and to 

 speak of them and the closely allied Thoracostei collectively 

 as the Scomberesocine series. For my own part, I do not 

 like the word Scomberesoces, because it implies relationships 

 which do not exist. On the other hand, the term Synen- 

 tognathi of American writers is equally inapplicable. 



Klein has shown (79, p. 120) that the opisthotic may be 

 absent in very diverse families of Teleosts^ and that even iij 



