388 TELEOSTEI 



the Elopidae, to which they are doubtless closely allied. The skeleton 

 differs in the absence of a gular plate, in the partial or complete with- 

 drawal of the maxilla from the margin of the mouth, which is small, 

 in the presence of a third, pterotic, branch to the post- temporal, in the 

 articulation of only two radials with the coracoid, and in the larger size 

 of the postclavicle, which is formed of three pieces. The parasphenoid 

 is expanded, and bears numerous grinding teeth opposed to a similar 

 patch of teeth on the basibranchials (Figs. 330-31). Two rows of valves 

 remain in the conus (p. 363). 



Albula has a flattened transparent larva very similar to the Lepto- 

 cephalus larva of the Anguillifornies. 



Albula, B. and S. (Butirinus) ; tropical seas. Anoymius, Cope ; 

 Cretaceous, N. America. Pterothrissus (Bathythrissa), Hlg., deep-sea, 

 Pacific. 



Family MORMYRIDAE. A most remarkable family of freshwater 

 African fish, highly specialised in some respects. In the Mormyrinae 

 the head may become drawn out into a long decurved sriiout carrying 



FIG. 378. 

 Mormyrus oxyrhynchus, Geoff. (After Giinther.) 



the small mouth at its extremity, and sometimes provided with a ventral 

 appendage (Fig. 378). The premaxillae fuse and the maxilla, palatal, 

 and pharyngeal bones are toothless. The large scale-like supratemporal 

 covers a wide lateral fossa. The opisthotic, symplectic, entopterygoid, 

 and supramaxilla are absent. The hyopalatine arch is firmly fixed to 

 the skull, the palatine being fused to the vomer. Paired tendon bones y 

 comparable to those of Polypterus, project backwards from the hypo- 

 branchials. The suboperculum is small, concealed below the operculum, 

 or absent. The branchial opening is narrowed. Diverticula are given 

 off by the air-bladder to the auditory capsules, and the bladder is cellular 

 in Gymnarchus. A peculiar diverticulum grows on the bulbus arteriosus. 

 The brain of these fish is remarkable for its large size, owing chiefly 

 to the great dorsal development of the tuberculum impar and vagus 

 centres. A thick glandular skin covers the head and even the eyes, which 

 are often somewhat degenerate. In most genera the caudal region is 

 long, and the anal fin considerably lengthened ; Gymnarchus acquires an 

 eel-like shape with tapering tail, while the pelvic, anal, and caudal fins 

 disappear. 



All the Mormyridae seem to have electric organs developed in the 



