2052 Bulletih 47, United States National Museum. 



766. LEPTAGONUS, Gill. 



Leptagonus, GILL, Proc. Ac. Nat. Sci. Phila., xin, 1861, 167, 259 (spinosissimus^decagonus). 

 Body tapering, depressed; head about 5; depth 7i to 9; width 6 to 8 

 in total length. Plates in dorsal series 40 to 44 ; 5 to 6 pairs between occi- 

 put and first dorsal; both dorsals present; mouth inferior, snout much 

 projecting; teeth on both jaws, probably none on vomer or palatines; 5 

 pairs of barbels about mouth; none under tip of snout; 1 pair of recurved 

 spines at tip of snout ; 1 pair of supraocular and I pair of occipital spines. 

 Gill membranes joined to isthmus. (ksTtros, slender; Agonus.) 



2408. LEPTOGONUS DECAGONUS* (Bloch & Schneider). 



Br. 6; D. V to VII, 5 to 8; A. 6 to 8; P. 14 to 16; Y. I, 2; C. 24. Body 

 distinctly more slender than in A. cataphractus; its greatest breadth, over 

 base of pectorals, about 6| to 8 times, and greatest height, at the third 

 pair of dorsal plates, about 71 to 9 in total length, hence but little de- 

 pressed. Vent nearer base of ventrals than in A. cataphractus; about 2 

 pairs of plates from vent to ventrals (no plates medially between them), 

 and 9 pairs from vent to anal fin. Distance from tip of snout to vent about 

 4 in total length. Body anteriorly nearly oval, angular; abdominal 

 region relatively shorter and tail, relatively longer than in A. cataphractus. 

 Body octagonal ; tail hexagonal, depressed, its ventral keel quite prominent. 

 Ridges on plates of body and their backwardly directed spines more prom- 

 inent than in A. cataphractus. Keels of the superior and inferior lateral 

 series especially sharp on tail; 5 or 6 pairs of plates from head to first 

 dorsal, and 10 to 13 pairs between ventrals and anal; from anterior end of 

 first dorsal to point of union of the dorsal pairs behind second dorsal 

 about 22 pairs, thence to base of caudal 14 to 17 median plates. Head 

 about as broad as deep, the breadth about 1-J- in its length ; head about 5 

 or somewhat more in total length, much narrowed anteriorly. Snout pro- 

 jecting beyond premaxillaries, lower jaw included; a pair of short 

 upwardly and backwardly directed spines near tip of snout; a pair of 

 strong supraocular and 1 of occipital spines; interorbital space consid- 

 erably less than longitudinal diameter of orbit; preorbital not covering 

 upper jaw; suborbital without prominent spine; no barbels under tip of 

 snout; mouth somewhat larger than in A. cataphractus y maxillary nearly 

 reaching anterior edge of orbit; 5 pairs of barbels, 1 near and 2 at tip of 

 maxillary, 1 near angle of mouth, and 1 (bifurcate) out on side on lower 

 jaw; none on branchiostegal membrane. Orbits quite large, their longi- 

 tudinal diameter about 4 in head. Preopercle with 2 quite small spines, 

 1 at its posterior angle, the other below this, and 1 or 2 smaller ones below 

 these; opercle unarmed. Branchiostegal rays 6. Teeth fewer than in 



,^ : . : ?. ^. taperin ^ octagonal aneror 

 pressed, its height 7* to 9, and its breadth 6} to 8 in 



head. Plates in dorsal series 44, sometimes 41-43; from occiput to rs orsa -; 

 rv T? ' a S ai l- an ^l 10-13; between dorsals 6 or 7; 5 pairs of barbels, 3 on maxil- 



tJ^fY V ai ! g e - Ot mouth ' and 1 (bifurcate) on lower jaw ; 1 pair recurved spines near 

 br P anLiTined tr?T^ 8Upra v U ^ r ^u * f occi P ital 8 P in es. Teeth on jaws. Gill mem- 

 ^2T?&?^ **', 1 



