THE AMERICAN TETRAGONOPTERINAE. 247 



Specimens examined. 



Catalogue 

 number specimens in mm. Locality Collector 



20768 part - ^-^'P*" ] 11 [ Tabatinga Bourget 



( Paratype 1 70 ) 



Allied to A. asynunetricus, distinguishable from all other species by the 

 anterior position and sublinear character of its humeral spot. 



Head 3.5; depth 2.8; D. 11; A. 28-32; scales 9.5 or 10-52 or 53-6 ; eye3 + ; 

 inter orbital 3. 



Compressed; elUptical to the caudal peduncle; profile shghtly depressed 

 over the eye. Preventral area rounded, without a median series of scales; post- 

 ventral area compressed to a narrow edge. Predorsal area compressed to a keel, 

 the median Une naked in front, some of the scales with the edge turned over the 

 ridge near the dorsal, no median series of scales. 



Occipital process about 5 in the distance from its base to the dorsal, bor- 

 dered by 4 or 5 scales on the sides. Anterior fontanel but little shorter than 

 the posterior, exclusive of the groove on the occipital process. Interorbital 

 scarcely convex. Second suborbital leaving a considerable naked area which 

 is widest below. Four to six teeth in the front row of the premaxillary, the 

 third tooth, or if there are six teeth, the fourth out of line; five teeth in the 

 second row, their denticles in a slightly curved line. Maxillary with one or 

 two minute teeth. Mandible with four large teeth and numerous smaller ones. 



Gill-rakers 8 + 14, about half the length of the orbit. 



Scales regularly imbricate, the rows not deflected over the anal, no auxiliary 

 rows; each scale with several subparallel lines; scales largest above the pectorals 

 where the height of their exposed edge is nearly twice its length. Caudal naked, 

 anal sheath of a single series of caducous scales. Lateral line but Uttle decvirved, 

 the row of scales below it parallel with it ; axillary scale well developed. 



Dorsal pointed, its origin equidistant from tip of snout and caudal, its 

 height 3.6-4 in the length. Caudal lobes 3.5 in the length. Origin of anal 

 and first scale behind dorsal equidistant from tip of snout. Anal emarginate. 

 Ventrals and the second scale in front of the dorsal equidistant from tip of 

 snout, their tips just reaching anal. Tips of pectorals beyond origin of ventrals 

 but not to end of axillary scale. 



A silvery lateral band about one third as wide as eye; a horizontal black 

 spot one fourth as wide as eye and rather longer than eye, beginning on the 

 upper part of the fii'st scale of the lateral line and extending straight back, 

 pointed behind ; middle caudal rays black; otherwise plain. 



