2876 Bulletin //, United States National Museiim. 



NN. Pectorals not normally formed. 

 O. Pectorals undivided, subiiumeral; p8eudobrancliia> absent. 



LXX, Benthosaukid.e, 543. 

 OO. Pectoral rays elongate, arranged in two groups. 



LXXI, Bathypteroidiixe, 544. 

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

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



LXXVIII, ASTRONESTHID^, 586. 

 PP. Barbels none. 

 Q. Vertebral spines projecting through skin of back before dorsal 

 fin; body short and deep, greatly compressed. 



LXXXIV, SXERNOPTYCHIDyE, 603. 



QQ. Vertebral spines not exserted in front of dorsal. 

 R. Pseudobranchiic present. 

 S. I'remaxillaries forming eutire margin of upper jaw; body scaly; 



opercles complete. 

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



very small LXXXIII, Paralei'II>id.e, 599. 



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

 spicuous LXXV, MYCTornii>.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. Pseudobranchije absent; mouth large, with canine teeth ; scales 

 deciduous or wanting.. .LXXVII, Ciiauliodontid.e, 578. 

 AA. Back without adipose fin. 

 B. Back with a single dorsal fin made u]) 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, Poi.yodontiike, 101. 



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



preceded by 4 barbels XXXI, Acipen.serid,!:, 102. 



DBB. 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. 



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



/. Barbel free at tip LXXIX, Stomiid e, 587. 



//. Barbel connecting throat with symphysis of lower jaw. 



LXXX, Malacosteid.e, 592. 

 TIH. Throat without barbel. 



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



small CI, FisTUEARiiD.E, 755. 



J J. Caudal fin without filament. 

 K. Pectorals present. 

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



XXXVIl, Cyphinid.e, 199. 

 LL. Gill membranes free from isthmus ; opercles incomplete. 



LXXIII, ROXDKl.KTIIIXE, 547. 



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



LXXXV, IDIACANTHID.E, 604. 



G(i. Body scaly. 



