2876 Bulletin tf, United States National Museum. 



NN. Pectorals not normally formed. 

 O. Pectorals undivided, subhumeral ; pseudobranchiae absent. 



LXX, BENTHOSAURID,E, 543. 

 OO. Pectoral rays elongate, arranged in two groups. 



LXXI, BATHYPTEROIDID^E, 544. 



DD. Sides of body with photophores more or less developed. 

 P. Barbel at throat present, very long ; body naked. 



LXXV1II, ASTRONESTHID^:, 586. 

 PP. Barbels none. 



Q. Vertebral spines projecting through skin of back before dorsal 

 fin; body short and deep, greatly compressed. 



LXXXIV, STERNOPTYCHID.E, 603. 

 QQ. Vertebral spines not exserted in front of dorsal. 

 R. Pseudobranchire present. 

 S. Premaxillaries forming entire margin of upper jaw; body scaly; 



opercles complete. 



T. Form elongate, the snout pointed, barracuda-like ; photophores 

 very small ................ LXXXIII, PARALEPIDID.E, 599. 



TT. Form oblong, the snout not much produced ; photophores con- 

 spicuous ..... . ................ LXXV, MYCTOPHID.E, 550. 



SS. Premaxillaries not forming the whole margin of upper jaw, the 

 maxillary entering into it; body naked; opercular appa- 

 ratus incomplete .... ........ LXXVI, MAUROLOCID^E, 576. 



RR. Pseudobranchise absent; mouth large, with canine teeth; scales 

 deciduous or wanting.. .LXXVII, CHAULIODONTID^, 578. 

 AA. Back without adipose fin. 



B. Back with a single dorsal fin made up of rays and not preceded 



by a series of free spines or followed "by finlets. 



C. Tail evidently strongly heterocercal. 



D. Body naked ; snout with a spatulate blade ; mouth wide, without 



barbels ...................... XXX, POLYODONTID^E, 101. 



DD. Body with 5 series of body shields; mouth, inferior, toothless, 

 preceded by 4 barbels ........ XXXI, ACIPENSERID.E, 102. 



DDD. Body scaly. 



E. Scales cycloid ; a broad bony gular plate ; dorsal fin many rayed. 



XXXIII, AMIID.E, 112. 

 EE. Scales ganoid ; no gular plate ; dorsal fin short. 



XXXII, LEPISOSTEID.E, 108. 

 CC. Tail not evidently hetorocercal. 



F. Tail tapering to a point, without caudal fin ; anal fin very long, 



of about 200 rays ; body scaly. 



LXXXVI, HALOSAURID.E, 606. 

 FF. Tail not tapering to a point; caudal fin developed. 



G. Body naked. 



H. Throat with a long barbel ; no caudal filament ; mouth large. 

 J. Barbel free at tip ...................... LXXIX, STOMIID.E, 587. 



II. Barbel connecting throat with syniphysis of lower jaw. 



LXXX, MALACOSTEID^E, 592. 

 HH. Throat without barbel. 



J. Caudal fin with a long filament; body elongate; mouth very 

 small ............................. CI, FISTULARIID^E, 755. 



JJ. Caudal fin without filament. 

 K. Pectorals present. 

 L. Gill membranes joined to the isthmus; opercles complete. 



XXXVII, CYPRINID^E, 199. 

 LL. Gill membranes free from isthmus ; opercles incomplete. 



LXXIII, RONDKhETIID.E, 547. 



KK. Pectorals wanting; body snake-like; dorsal long and low. 



LXXXV, IDIACANTHIDJS, 604. 



GG. Body scaly. 



