Classification of the Order Apodes. 379 



Simenchelidffi, Ilyophid^, and Dyssomidas^ Giintlier'rf arrange- 

 ment (Cat. Fish. viii. p. 19) is the one still in general use 

 {cf. Jordan & Eveiniann, ' Fisiies of N. A.nierica,' p. 345). 



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

 242) has added considerably to our knowledge of the diagnostic 

 characters of the Anguillida3, Simenchelidge^ Synapho- 

 branchidse, Mursenesocidse, and Muraenidse. JV|^lie. Popta 

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

 pharyngeals in a number of types. 



Synopsis of the Families. 

 I. Caudal fin free 1, Ureticheliche. 



II. Caudal fin, when present, continuous with dorsal aud 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. 



». Pharyngeals oblong- or ovate, covered with small teeth j 

 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. Amjtdllidce, 

 Mouth transverse ; 4 pectoral radials 3. Simenchelidcu. 



** Pharyngeal openings of branchial clefts narrow. 



Palato-pterygoid an elongate lamina ; no pec- 

 toral fins 4. X.enocon(jridce. 



Palato-pterygoid very slender, almost vestigial ; 



pectoral tins present 5. Myrocongridce. 



/3. Upper and lower pharyngeals with strong biserial teeth, 

 elongate, supported by the enlarged fourth epi- and 

 cerato-branchials ; caudal vertebrae with transverse pro- 

 cesses ; pharj'ngeal openings of branchial clefts narrow ; 

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

 toral fins 6. Miircenidce. 



h. Prootic and basioccipital forming a prominent bulla ; eyes 

 very small ; vertical fins well developed only near end of 

 tail ; 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* 



