SOUTH AMERICAN NEMATOGNATHI. 355 



ss. Lower surface of the tail flat, the plates covered with skiii; 

 six or seven azygous plates in front of the adipose spine; 

 marginal spines strongest forward, none on the interopercle. 

 t. Dorsal long, I, 9 or 10, the last ray adnate; plates exposed 

 at base. Delturus xc. 



it. Dorsal short, I, 7, the last ray free; basal portions of 

 plates concealed by membrane; a naked area behind dorsal 

 fin. Hemipsilichthys xci. 



rr. Adipose fin none; lateral plates entirely isolate; back be- 

 hind dorsal fin with large plates. Acanthicus xcii. 

 jjj. Margin of the snout naked, without bristles, granules or tenta- 

 cles; interopercle with erectile spines. Ch^tostomus xciii. 

 jjjj. Margin of the snout with tentacles; sometimes naked in fe- 

 males; ventral surface naked; interopercle with a bunch of spines 

 inserted on a movable plate. Ancistrus xciv. 



Subfamily LORICARIIN^. 

 LXI. Farlowella. 



Acestra Kner, Panzerwelse, 93, 1853 (sp.), preoccupied 

 in Hemiptera Dall, 1852. 



Farlowella Eigenm. & Eigenm. Proc. Cal. Acad. 2d 

 Ser. ii, 32, 1889. (acu.^.) 



Type: Acestra aciis Kner. 



Very slender, elongate; snout narrow, produced; dor- 

 sal fin inserted at least partially over the ventrals. Six 

 or more large plates between the occipital and the dorsal. 



Habitat: Amazon and its tributaries; Caracas. 



The species of this genus are the extremes in slender- 

 ness and in the prolongation of their snouts. 



ANALYSIS OF THE SPECIES OF FARLOWELLA. 



a. Upper angle of gill-opening nearer beginning of dorsal than to tip of 

 snout. 

 b. Snout with smooth or granular plates. 



c. Belly with two series of longitudinal plates. 



d. A. 4; space between cavity of mouth and base of pectoral with 

 four longitudinal rows of scutes arranged in three transverse 

 series; maxillary barbel short. Eye 3 in interorbital. Scutes 

 with small graniilations longitudinally arranged. Head to tip of 

 occipital scarcely more than one-third of the length. Caudal lit- 

 tle developed. Outer rays of the fins with brown dots. D. I, 6; 

 P. I, 5; V. I, 4; Lat. 1. 34. (Gtinther.) yladiola 295. 



