22 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



relatively slight and almost entirely comprises the exoccipital and 

 prootic. In Microbrotula, the expansion is greater but comprising the 

 same two bones. In another brotulid, "Dinematichihys" (see Gosline, 

 1953), in Benthocometes robustus (see Bougis and Kuivo, 1954, fig. 17), 

 and apparently in the carapid "Fierasjer acus" (see Emery, 1880), 

 the intercalar forms a part of the bulla wall. 



One seems to be on fairly firm ground in associating auditory 

 bulla expansion with some specialization in hearing though, to my 

 knowledge, the exact nature of the association remains unknown. 

 It is probably more controversial to attempt to relate the gas bladder 

 peculiarities of ophidioids with hearing; however, I agree with Marshall 

 (1965, p.. 314) that there is such a relationship. In the ophidioids 

 except Gadopsis, there always appears to be ligamentous tissue 

 extending between the anterior end of the gas bladder and the anterior 

 ribs, one or more pairs of which are modified considerably (Regan, 

 1903b; Arnold, 1956). In the ophidiids (Rose, 1961) and oviparous 

 brotulids (Marshall, 1965, p. 314 quoting Courtenay, in litt.), it has 

 been suggested that the ligaments to the forward end of the gas 

 bladder are used in sound production. 



Something should be said at this point about the Carapidae and 

 Pyramodontidae. These families, most if not all the members of which 

 live as inquilines in the cavities of invertebrates, generally are agreed 

 to be related to the brotulids and ophidiids. Among the numerous 

 features probably associated with their mode of life, however, are the 

 loss of the pelvic fins and the development of a more or less terminal 

 mouth, often with enlarged teeth. The other systems dealt with above 

 seem to be essentially the same as those in the brotulids and 

 ophidiids. 



To summarize briefly the sensory systems and related structures in 

 the ophidioids, these fishes seem to have become modified extensively 

 in association with the development of filamentous pelvics that are 

 used presumably as probes for finding food. Though various fishes 

 have developed similar probes from other structures, the gadoids, 

 ophidioids, some anabantoids, and pegasids are, to my knowledge, the 

 only fishes that have developed filamentous pelvics of this type. By 

 contrast, the hypertrophy of the acustico-lateralis system and the 

 degeneration of the eyes have occurred repeatedly, especially among 

 deep-sea forms. (Whether these features are brotulid preadaptations to 

 or have been developed in association with a deep-sea existence has 

 no bearing on the present argument.) The unique feature, presumably 

 associated with the acustico-lateralis system, that the ophidioids seem 

 to have developed is the gas bladder-rib relationship. 



In the following paragraphs no attempt will be made to give any 

 complete structural account of Gadopsis or other ophidioids. Regard- 



