CLUPE I FORMES 



389 





caudal muscles ; they are especially powerful in Gymnarchus. This genus 

 is also remarkable for its larval stage with a large yolk-sac and external 

 gills (Fig. 379, Budgett [67a], Assheton [20]). All African. 



Sub-Family MORMYRINAE. Differs from Gymnarchus in having a simple 

 air-bladder, toothed parasphenoid and glossohyal, special bones alongside 

 the electric organs, a foramen 



in the scapula, or between it ^ 



and the coracoid, and complete 

 fins. 



Mormyrops, J. M. ; Petro- 

 cephalus, Marc. ; Mormiirn*, 

 L. ; Gnathonemus, Gill ; Stoma- 

 torhinus, Blgr. ; Marcuson'm, 

 Gill. 



Sub - Family GYMNAR- 

 CHIDAE. Gymnarclms, Cuv. 



Family HYODOXTIDAE. 

 Hyodon seems to be related 

 both to the Notopteridae and 

 to the Mormyridae. It differs 

 from the latter in possessing 

 a wide mouth, with strong 

 teeth on the maxillae as well 



as the premaxillae, a symplectic, and in the absence of a closed ovisac 

 (p. 368). There is the same lateral temporal fossa covered over by an 

 expanded supratemporal, and vesicle of the air-bladder, which here lies 

 against a fenestra of the auditory capsule. The pterygoids are separate, 

 and the hyopalatine arch movably articulated. A prominent toothed 



FIG. 370. 



Larva of '///""''v'i'.< nHoi'tru*, Cuv. (After Budgett, 

 Trant. Zool. Soc.) 1, yolk-sac; _', external gills ; 3 

 and 4, subintestinal vein. 



FIG. 380. 



Koto]>t' r* l;j>ii-nt, Luc. (After Day, Fishes o/Iii'lin.) 



ridge is formed by the parasphenoid. The very large coracoids meet 

 ventrally in a keel. The body is elongate and compressed. 



Hyodon, Le S. ; rivers of N. America. 



Family NOTOPTERIDAE. Another small family, allied to the two last. 

 These highly specialised fish have a very compressed body, a very short 

 trunk followed by a long tapering caudal region, with a dorsal fin small 

 or absent. The tail is gephyrocercal, and the caudal fin continuous with 

 the very long anal (Fig. 380). The pelvic fins are reduced or absent. 



