50 MEMOIRS OF THE CARNEGIE MUSEUM. 



large, cheeks below the eye entirely covered, the part behind the eye mostly naked. 

 Form compressed; fins large, origin of anal under dorsal; adipose fin well-developed, 

 anal truncate or with a narrow lobe; caudal naked; lateral line incomplete; scales 

 with a few diverging strise. 



It is quite possible that the species here included in one genus should be dis- 

 tributed to other genera. It is certain that the species selected as the type is 

 generically different from any of the other genera recognized in this paper. As 

 stated above melanotus may belong to Macropsobrycon, with which the present 

 genus is very closely related.* 



Key to the Species of Megalamphodus. 



a. Anal with a narrow lobe, 25-27; depth 2.2-2.4; fourth dorsal reacliing caudal; a very conspicuous humeral 



bar; dorsal dark, without a distinct spot; about twenty maxillary teeth ... 24. megalopterus Eigenmann. 



aa. Anal truncate, the rays graduate; dorsal not falcate in the specimens examined. Maxillary with two to six 



teeth. 



b. A. 30; depth 2.5; a conspicuous humeral band; most of the dorsal black; anal margined with black. 



25. eques Steindachner. 



66. A. 25-28; depth 3.8; premaxillary with about twelve teeth; maxillary with about four teeth, its 



length equal to that of the eye; dorsal with a dark spot; a faint humeral spot and a faint caudal spot. 



26. melanotus Eigenmann. 

 666. A. 27-30; depth 3; no humeral spot; upper half of the first five developed rays of the dorsal black; six 



maxillary teeth. 27. heteresthes Ulrey. 



6666. A. 24-26; depth 2.4; sides uniformly dusted or with a narrow humeral bar; all but the first and the 

 last three or four dorsal rays black; caudal and anal margined with black; maxillary with two to six 

 teeth 28. micropterus Eigenmann. 



24. Megalamphodus megalopterus Eigenmann sp. nov. (Plate VII.) 



6806, C. M., type, 35 mm. 6807a-b, C. M., paratypes, 3, largest 34 mm. 

 Caceres, May 23, 1909. Haseman. 



Head 3.5; depth 2.2-2.4; D. 11; A. 25-27; lateral line 32-35, 4 to 6 scales 

 with pores; eye 2.5, slightly greater than interorbital. 



Greatly compressed, ventral outline regularly curved; dorsal outline steep 

 to the dorsal, with a slight depression over the eye, base of dorsal very oblique; 

 depth of caudal peduncle equal to its length; predorsal area narrow, with a regular 

 series of nine or ten scales; preventral area broad, covered with two series of scales 

 overlapping along the median line with an occasional scale at their angles. Fon- 

 tanels both very large, anterior end of frontal fontanel equidistant from tip of 

 snout and its posterior end; parietal fontanel much wider than the frontal; occipital 

 process extending more than one-fourth to the dorsal. Mouth very oblique, 

 maxillary as long as eye, reaching to suture between second and third suborbitals; 



* For additional species see Appendix to this article. 



