150 MEMOIRS OF THE CARNEGIE MUSEUM 



Megalonema gen. nov. 



Megalonema Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 383 



(name only). 



Type, Megalonema platycephalum sp. nov. 



Pimelodines without teeth on vomer, the pectoral and dorsal spines prolonged 

 into filaments, articulate, not pungent; barbels flattened, not fringed; premaxillary 

 band of teeth without backward projecting angles; occipital process narrow, not 

 reaching dorsal plate; caudal deeply forked; eye in middle of head. 



27. Megalonema platycephalum sp. nov. (Plate X, fig. 2.) 

 Megalonema platycephalum Eigenmann, Repts. Princeton Univ. Exp. Patagonia, 



III, 1910, 383 (name only). 



Type, 173 mm. Tumatumari. (Carnegie Museum Catalog of Fishes No. 

 1684a.) 



Cotypes, four specimens, 37-65 mm. Tumatumari. (C. M. Cat. No. 1685a; 

 I. U. Cat. No. 12060.) 



Head 3.66; depth 5.5, D. 1,6; A. 11; eye 2 in snout, 5 in head, equal to 

 interorbital. 



Triangular in section at the dorsal, becoming oval at the caudal peduncle; 

 profile nearly straight descending to the snout, ventral profile straight. 



Fig. 31. Outline of premaxillary band of teeth in Megalonema platycephalum Eigenmann. 



Head rounded at the occiput, flat between the eyes; occipital process spine- 

 like, not quite reaching the dorsal plate; a pair of ridges from in front of the max- 

 illary barbels converging to the base of the occipital process; fontanel not continued 

 to the posterior margin of the eye; upper jaw projecting the width of the premax- 

 illary band of teeth; snout broad, depressed, width of mouth equals half the length 

 of the head; width of premaxillary band of teeth 7 in the length of its outer margin, 

 its outer ends rounded. 



Maxillary barbel reaching tip of anal; outer mental barbel reaching tip of inner 

 pectoral ray; the mental barbels some distance in advance of the outer or post- 

 mentals, reaching base of pectorals; gill-membranes broadly overlapping, separate 

 to below the angle of the mouth. 



Dorsal spine slender, articulate above, as long as the head, the rays decreasing 



