Classification of the Order Apodes. 379 



Simenchelidse, Ilyophidas, and Dyssomidse, Giinther's arrange- 

 ment (Cat. Fish. viii. p. 19) is the one still in o;eneral use 

 [cf. Jordan & Evermaun, ' Fishes of N. ALtiierica,' p. 345). 



Gill (Proc. U.S. Nat. Mus. xiii. 1890, pp. 157-170, 231- 

 242) has added considerably to our knowledge of the diagnostic 

 characters of the Anguillid?e, Simenchelideej Sjiiapho- 

 branchidae, Murjenesocidse, and Muvaenidse. Mile. Poptq, 

 (Ann. Sci. Nat. (8) xix. 1905, p. 367) has described the 

 pharyngeals in a number of types. 



Synopsis of the Families. 

 I. Caudal tin free 1. Uretichelidce. 



II. Caudal fin, when present, continuous with dorsal atid anal ; no 

 pelvic fins. 

 A. Frontals pau-ed, united by suture. 



1. Jaws not produced, the snout conical or obtuse. 

 a. Otic bulla little inflated. 



a. Pharyngeals oblong or ovate, covered with small teeth ; 

 caudal vertebrae without transverse processes. 

 * Pharyngeal openings of branchial clefts wide ; palato- 

 pterygoid well developed ; pectoral fins present. 

 Mouth with lateral cleft ; 8 pectoral radials .. 2. Anyuillidce. 

 Mouth transverse ; 4 pectoral radials 3. Simenchelida. 



** Pharyngeal openings of branchial clefts narrow. 



Palato-pterygoid an elongate lamina ; no pec- 

 toral tins 4. Xenocongridce. 



Palato-pterygoid very slender, almost vestigial ; 



pectoral fins present 5. Mijrocongridce. 



j3. Upper and lower pharyngeals with strong biserial teeth, 

 elongate, supported by the enlarged fourth epi- and 

 cerato-brancbials ; caudal vertebrae with transverse pro- 

 cesses ; pharyngeal openings of brancbial clefts narrow ; 

 palato-pterygoid very slender, almost vestigial ; no pec- 

 toral fins ." 6. Murcenidce. 



h. Prootic and basioccipital forming a prominent bulla; eyes 

 very small ; vertical fins well developed only near end of 

 taif; pectorals vestigial or absent. 

 Heart just behind gills; palato-pterygoid well 

 developed ; pharyngeal openings of bran- 

 chial clefts wide ' 7. Heterenchelidce. 



Heart far behind gills ; palato-pterygoid ves- 

 tigial ; pharyngeal openings of inter- 

 branchial clefts narrow 8. Moringuidce. 



2. Jaws much produced, the snout long and slender; no palato- 



pterygoid ; pharyngeal openings of branchial clefts wide. 

 Suspensorium vertical ; vent near gill-openings 

 and tail very long; vertebrae very nume- 

 rous 9- Nemichthyidce. 



26* 



