272 SILTTRID-B. 



obliquely rounded ; adipose fin confluent with caudal ; ventrals in- 

 serted below the dorsal. 

 Rio de la Plata. 



109. NEMATOGENYS. 



Nematogenys, Girard, in Proc. Acad. Nat. Sc. Philad. 1854, p. 198. 



Adipose fin none. Dorsal fin short, placed in the middle of the 

 height of the body, above the ventral fin, without pungent, spine ; 

 anal short; caudal rounded. Teeth villiform, forming a band in 

 both jaws ; palate toothless. Barbels six : two to the nostrils, one 

 to each maxillary, and a pair to the mandible. Eyes small. Head 

 covered with soft skin, not armed. Gill-openings rather wide, sub- 

 contiguous at the throat. Ventrals six -rayed. 



Chile. 



1. Nematogenys inermis, 



Trichomycterus inermis, Guich. in Gay, Hist. Chil. Zool. ii. p. 312, 



Ail. Ictiol. lam. 9. fig. 2. 

 Nematogenys inermis, Girard,in U.S. Nav. Astron.JExped.Zool.ip.240. 



pi. 32. 



B. 12. D. 10. A. 11. P. 1/7. V.. 6. 



The maxillary barbels extend to, or somewhat beyond, the base of 

 the pectorals ; nasal barbels shorter than those of the mandible. 

 Yellowish, with numerous blackish spots. 



Chile. 



Sixteenth Group. TRICHOMYCTERINA. 

 The rayed dorsal fin is behind the ventrals, if the latter are 

 present. 



110. TRICHOMYCTERUS*. 



Trichomycterus, Valenc. in Humb. Observ. Zool. ii. p. 347. 

 Pygidium, Meyen, Reke, i. p. 475 ; Wiegm. Arch. Naturgesch. 1835, ii. 

 p. 269. 



Adipose fin nonet- Dorsal fin short, without pungent spine, placed 

 behind the middle of the body, and behind the ventral fins ; anal 

 short ; caudal truncated. Teeth villiform, in broad bands in the 

 jaws ; palate toothless ; cleft of the mouth rather narrow, with a 

 pair of maxillary barbels on each side; a pair of slender nasal 

 barbels. Eyes small, directed upwards. Head covered with soft 



* 1 . Trichomycterus incse, Cuv. $ Val. rviii. p. 496. — Rio Guatanai. 



2. pen tlandii, Casteln. Anim. nouv. Amir. Sud, Poiss. p. 49. pi. 24. fig. 1. 



— Near Sarayacu. 



3. punctatissimus, Casteln. I.e. fig. 3. — Araguay. — -In the two last species 



the dorsal fin would appear to be placed above the ventral, if the figures 

 be correct. 



t A series of rudimentary caudal rays extends forwards towards the dorsal 

 and anal fins, and is covered with fat in well-fed individuals. 



