94 Memoir Sears Foundation for Marine Research 



characterizes the living holosteans; and (5) a well-developed articulation with the 

 autopalatines in elopids. Indeed, in the development of the whole upper jaw mechanism, 

 the elopoids are considerably in advance of the holosteans. 



However, though we accept the traditional view that the elopids and albulids 

 (with Pterothrissus) do belong among the Isospondyli, there is much uncertainty as to 

 their disposition within that Order. For example, Jordan and Evermann (2J: 407), 

 followed by Norman (jj: 63), rated them as families within the Suborder Clupeoidea; 

 Berg (4: 221, 222; 419,420) defined them as superfamilies (Elopoidae and Albuloi- 

 dae), each to include two families; Fowler (j6: 151) and Poll (j6: 8) rated them as 

 families of Isospondyli (Clupeiformes of Poll) without the intervention of Suborders. 

 However, as early as 1893, Gill (77: 127—128) made them the basis of a separate Sub- 

 order, Elopoidea, in which he was followed by Bertin and Arambourg {18: 22 11), 

 who stressed in particular the primitive nature of their caudal fin skeleton.-* Jordan 

 {22: 117— 118), proceeding a step further, proposed the Suborder Elopoidea for the 

 elopids and the Suborder Albuloidei for the albulids as contrasted with the clupeoids 

 and with other Suborders of Isospondyli; Matsubara-^ has also accepted this arrange- 

 ment. 



Exclusion of the elopids and albulids from the clupeoids clearly seems demanded, 

 for among living fishes they appear to stand much lower on the evolutionary tree than 

 any other teleosts that are at all well known. But it still remains an open question whether 

 the features in which the elopids and albulids agree, balanced against those in which 

 they differ, are better represented by placing them in two separate Suborders or by 

 uniting them in one, as is done here. 



The isospondylids as here defined include the ladyfishes or bigeye herrings, the 

 tarpons, the bonefishes, the true herrings, the anchovies, and the salmons, all of which 

 have been familiar for generations to seaside dwellers in general in one part of the world 

 or another. They also include such of the pikes as enter brackish or salt water, and 

 an assemblage of oceanic fishes, many of which have luminescent organs and are 

 bizarre in appearance; the latter are seldom seen by ordinary seafarers, commercial 

 fishermen, or anglers, and little is known about their mode of life. 



Key to Suborders. Although the general characteristics are now tolerably well 

 known for the elopoid, herring-like, salmon-like, and pike-like fishes, we still have so 

 much to learn about the internal anatomy of the less familiar groups of Isospondyli 

 that their natural affinities remain obscure in many respects. Areas of continuing un- 

 certainty are, for example: the relative weights to be accorded one character or 

 another from the evolutionary standpoint; the breadth of coverage to be allotted to 

 the herring-like fishes and the salmon-like fishes; and the disposition to be made of 

 various outlying families such as the Bathylaconidae (Part 4), which do not readily fit 

 in any of the major subdivisions that are recognized generally. Furthermore, Suborders 



Z4. For accounts of the caudal fin skeletons of Elops, Albula, and Megalops, see Regan [jtj : 355, 356, fig. i) ; see Hollister 



{21: 260-276) for Etops and Albula. 

 25. Elopina and Albulina, Suborders of Order Clupeida (equivalent to Isospondyli) (27: 180-182). 



