GREGORY: FISH SKULLS 



321 



The setting apart of the echeneids as a distinct "order" Discocephali, solely on account 

 of their possessing this specialized structure, the sucking-disc, assuredly contributes little 

 to the question of the phylogenetic relationships and origin of the group. Finally, the 

 echeneids afford a good example of a group which has acquired one marked regional spe- 

 cialization, with only minor modifications of the rest of the body, in contrast with such a 

 form as Mola, in which all parts of the body have become profoundly specialized. 



ucking' disk 



EcheneLs n a aerates 



Fig. 199. Echeneis. Side view. Sucking-disc seen obliquely from below. 



Postscript. — The recent studies of Mr. G. Allan Frost on the otoliths of Neopterygian 

 fishes may possibly afford a clue to this long-standing puzzle. He states (1930(3, p. 621) 

 that the otolith of Echeneis naucrates is of the percid type and resembles that of Chromis 

 chromis of the family Pomacentridse, except in certain details; in one detail it resembles 

 that of Anableps tetrophthalmus of the order Synentognathi. 



Renewed examination of the skulls in question does not, however, reveal much evidence 

 in support of the possibility of Echeneis being related either to the pomacentrids or to the 

 Microcyprini. The entire skull, in top, side and bottom views, has been profoundly modi- 

 fied as a result of the presence of the modified dorsal fin so that the habitus has very largely 

 concealed the superfamily heritage. This fact gives a good example of the plasticity of the 

 fish skull and of the appearance of many coordinated, but pseudo-Lamarckian responses 

 of its various parts to the evolution of an organ lying outside of it. 



SCORP^NOIDEI (ROCK-FISHES, CoTTIDS, GuRNARDS, ETC.) 



It has long been recognized that the scorpaenoid or mail-cheeked fishes are closely allied 

 with the percomorphs, but they, being a large and diversified group with a very constant 

 leading character (the "suborbital stay"), have often been set off as a distinct order or 

 suborder, variously named Loricati, Pareiopliteae, Scleroparei, Scorpseniformes. 



