38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I42 



There seems little use in weighing the relative merits of these three 

 dividing lines. Still less is there any point in recognizing the groups on 

 either side of any of these lines in a formal classification. Each of 

 them merely represents a level of organization in a single structure, 

 M'hich, like fin spines, may have been attained independently several 

 times, or secondarily lost. (Nevertheless it is perhaps of some signifi- 

 cance that some fishes of questioned affinity, e.g., the sticklebacks, 

 always fall into a "higher" group in whichever of the three ways a 

 dividing line is drawn.) For the present, then, it seems most con- 

 venient merely to speak of the percoids and their derivatives as 

 "higher teleosts" and the isospondylous fishes and their derivatives 

 that have not attained the percoid phase as "lower teleosts." To adopt 

 this system, as is done here, has at least the advantage of attempting 

 to recognize phylogenetic rather than level-of-organization groupings. 



In further conclusion, a preliminary attempt will be made to carry 

 through the idea of phylogenetic groupings within the "lower" tele- 

 osteans. To start at the bottom with the isospondylous fishes, it 

 hardly matters for present purposes whether the group is polyphyletic 

 or not. In either event there seems to be a basic cleavage between a 

 //ioc?on-osteoglossoid group and the remaining isospondylous forms. 

 The /fjof/on-osteoglossoid section (division Osteoglossi of Gosline, 

 i960) seems to have given rise to the mormyrids and their allies. 

 The remainder (division Clupei), judging from the continuity of the 

 supraorbital-antorbital stay (section III), etc., would seem to have 

 given rise to most if not all other teleostean orders. 



As a second step it may be noted that there is a series of orders — 

 Clupeiformes, Halosauriformes, Notacanthi formes, and Cyprini- 

 formes — in which the basal members at least have the innermost 

 radial of the pelvic fin present as a separate nodule. There is another 

 group — Scopeli formes, Beloniformes, Percopsi formes, and Beryci- 

 formes — in which this same radial is fused to the base of the lower 

 half of the inner pelvic ray (section II). Now, this dift'erence is 

 neither of any great structural importance nor is it absolute. Never- 

 theless, those orders with a free inner radial all have the maxillary 

 typically included in the gape, whereas those orders with the inner ra- 

 dial and ray fused all have the maxillary excluded. Primarily on the 

 basis of this combination of characters it is here suggested that 

 there is a series of lower teleostean orders derived from the division 

 Clupei that never reached a scopeliform stage of evolution and another 

 series derived from the same source that did. (The eels must be in- 

 cluded in the former group even though today they have no pelvic 

 fins). 



