no. 3647 PERCIFORM FISHES — GOSLINE 21 



nerve location. In this connection, I propose the working hypothesis 

 that degeneration of the eye and its musculature is followed in time 

 by the loss of the myodome and the basisphenoid and that a longitu- 

 dinal trough bounded by membrane or bone and containing the an- 

 terior portion of the brain eventually will extend forward between the 

 orbits. Extreme examples of this sort of development are found par- 

 ticularly in such small-eyed, broad-headed fishes as the salmonoid 

 Galaxias, the gadoid Lota (Svetovidov, 1948), the zoarceoid Crypta- 

 canthodes (Makushok, 1961a), and the ophidioid "Dinematichthys" 

 (Gosline, 1953). 



In Gadopsis, as in ophidioids and numerous other fishes, the 

 basisphenoid is absent. The interorbital space has been encroached 

 upon from both the posterior and elsewhere. In Gadopsis the anterior 

 portion of the interorbital space is filled medianly in large part by a 

 crest rising from the parasphenoid (fig. 4). Above and behind this 

 crest is a V-shaped trough comprising a pair of membranes leading 

 upward and outward from the parasphenoid crest to attachments 

 on the lower surfaces of the frontals. At the posterior end of the 

 orbital cavities in Gadopsis, the internal orbital bony walls are ex- 

 tended anteromedially well beyond the trigemino-facialis opening 

 (fig. 4). 



In ophidioids, as in the gadoids and other fishes, the anteromedial 

 extension of the bony orbital rims is developed further. In Brotula, 

 for example, lateral flanges from the parasphenoid meet the frontals 

 ahead of the pleurosphenoid ("alisphenoid" of Regan, 1903b, p. 461, 

 fig. 1a). The latter bone, now completely surrounded by other 

 ossifications, seems to disappear completely in some brotulids. 



The olfactory organ of Gadopsis and ophidioids seems to be de- 

 veloped normally. In the forms examined, the two well-separated 

 nostrils on each side lead in over an elongate-oval rosette. In Gadopsis, 

 the olfactory nerve to each rosette passes back through the lateral 

 ethmoid and, for a short distance, through the anterior end of the 

 orbital cavity and alongside the parasphenoid crest. About one-third 

 of the way back in the orbits, the olfactory nerves of each side pass 

 into the membranous trough described above. They extend posteriorly 

 into this trough to the olfactory lobes of the brain, which project 

 forward into the trough. (Unlike many gadoids, the olfactory bulbs 

 of Gadopsis and ophidioids are at the front of the olfactory lobes of 

 the brain; see Svetovidov, 1948, pp. 13-17.) 



In the otic system of Gadopsis and ophidioids, there is always a 

 more or less enlarged auditory bulla. In the juvenile Gadopsis dissected 

 (106 mm SL), the wall of the central portion of this enlarged bulla is 

 membranous (fig. 4), and the intercalar (opisthotic) has only a 

 minute extension on it. In Brotula, the expansion of the bulla is 



