26 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



Caudal fin and skeleton. — Aside from the rounded shape, the 

 caudal fin of Gadopsis and its supporting structure (fig. 5a) seem to 

 be of a fairly normal percoid type. There are five hypurals (counting 

 as in Nybelin's 1963 system), one uroneural, and two epurals — all 

 autogenous — and 15 branched caudal fin rays. 



Among the brotulids, at least one member (Gosline, 1953) has 15 

 branched caudal rays, but there are more or less fusion and/or re- 

 duction in the caudal skeletons of all. In carapids, the caudal skeleton 

 and fin are absent. 



The caudal fin of the gadids has been the subject of much discussion. 

 The caudal skeleton at least seems to represent a modification from 

 a perfectly normal teleostean type (see, e.g., Barrington, 1936, and 

 Gosline, 1964) but so reduced as to be morphologically similar to 

 that of some brotulids. 



Summary. — To summarize Gadopsis, this fish seems in many 

 respects to present a mosaic of characters, some percoid and others 

 ophidioid. In the sense organs and associated structures, Gadopsis 

 seems to have developed most of the basic peculiarities of the 

 ophidioids: it has the anteriorly located, filamentous pel vies, the 

 subterminal mouth and jaw structure, the at least partially reduced 

 eyes, the expanded auditory bullae, and the troughlike sensory canals 

 of the head. In the following features, however, Gadopsis retains the 

 percoid condition rather than the more advanced ophidioid type: 

 the ramus lateralis innervation of the pelvics, the incomplete supra- 

 temporal commissure, and the simple gas bladder without special 

 relationships to the anterior ribs. 



In fin structure, aside from the pelvics, Gadopsis shows a generalized 

 percoid rather than the ophidioid condition. There are pungent 

 spines at the front of the dorsal and anal, three in the anal, with the 

 pterygiophore of the second extending in front of the first interhemal. 

 There are two predorsal bones. The caudal fin has 15 branched rays 

 and five autogenous hypurals. Finally, the dorsal and anal soft ray 

 relationship to vertebrae is percoid and does not show the crowding 

 of the rays found in ophidioids. 



In a few minor characters, Gadopsis is more specialized than at 

 least the more generalized ophidioids. It has no supramaxillary, and 

 the entopterygoid and ectopterygoid are fused. Perhaps into this 

 category should be added the fact that Gadopsis is a freshwater fish. 



The question arises as to whether or not Gadopsis should be retained 

 among the percoids or placed among the ophidioids. Zoologically, I 

 cannot see any clearcut basis for decision. From the viewpoint of 

 indicating the type of fish from which the ophidioids arose, Gadopsis 

 and the Gadopsidae perhaps can be allocated best to the ophidioids, 

 where the spiny-rayed Gadopsis would hold a position somewhat 



