SOUTH AMERICAN NEMATOGNATHI. 311 



mottled with darker, indistinctly striped; the fins in the 

 largest specimen margined with black, a white band 

 margining the black in the smallest specimen; dorsal fin, 

 inner surfaces of pectoral and ventral fins finely mot- 

 tled; a black axillary spot. 



Head 3*; depth 5; Br. 10-11; D. I, 6; A. 34. 



Two specimens .42-. 50 m. Serpa; Villa Bella. Thayer 

 Exped. 



246. Ageneiosus axillaris. 



A(n/uosus a:villaris Guuther, Cat. Fish. Brit. Mns. v, 431, 18G4 



(Surinam). 

 Habitat: Snrinam. 



This species is known only from the types. 



Family IV. HYPOPHTHALMID.E. 



=zSilurid(:c anomaloptercAi Giinther, Cat. Fish. Brit. 

 Mus. V, 3, 1864. 



=^Hyj)ophthalmidai Cope, Proc. A. A. A. S. 1871. 



This family composed of two genera, is confined to 

 the northern Amazon and Guiana region of South Amer- 

 ica. 



The anatomy of the family has been studied by Prof. 

 R. Ramsay Wright. * 



The characterization of the family is given in the key. 



ANALYSIS OF THE GENERA OF HYPOPHTHALMID^. 



a. Jaws and Yomer with teeth. Helogenes Iv. 



aa. Jaws and Yomer without teeth. Hypophthalmus Ivi. 



LV. Helogenes. 



Helogenes Giinther, Annals and Magazine Natural His- 

 tory, xii, 443, 1863 (marmoratus) . 



Type: Helogenes niarnioratiis Giinther. 



* On the Skull and Auditory Organ of the Siluroid Hypophthalmus, 

 Trans. Koy. Soc. Canada 1885, 107-118, plates viii-x. 



