66 THE AMERICAN CHARACIDAE. 



lateral line is complete in the specimens from some localities and incomplete 

 in those from other localities, or both types may be found in the same place. 

 The genus differs from Astyanax in having its caudal partly covered with minute 

 scales. It merges directly into the genus Hemigrammus which has an incom- 

 plete lateral line. 



Habitat. — Very abundant in Guiana and the Amazons, extending south 

 to the Paraguay and Parana Rivers and to the Rio Doce. It has not been 

 recorded from the Magdalena Basin from Central America, the western slope of 

 South America, or the lower reaches of the La Plata. 



Key to the Species. 



a. Depth considerably more than half of the length; much compressed. A. 33; scales 8-34-7. 



1. bondi Fowler. 

 to. Depth 2-2.66 in the length, sometimes 3.25 in M. costae. See also aaa. A. 23-36; Occipital pro- 

 cess one third to one fifth as long as the distance from its base to the dorsal. 

 6. Five or more scales between the lateral line and ventrals. 



c. Horizontal dark lines between the rows of scales; no caudal spot; humeral spot very long, 

 pointed in front. Median line behind occipital process sometimes covered by the bent over 

 margins of the scales along the side of the compressed back. Head 3.75; depth 2; A. 31- 

 36; scales 5| or 6-33 to 36-6; preventral area narrowly rounded; predorsal area sharply 

 keeled; occipital process two sevenths of the length from its base to the dorsal; origin of 

 ventrals equidistant from tip of snout and origin of last third of anal. 



2. latissima Eigenmann. 



cc. No horizontal dark lines; seven scales between dorsal and lateral line; ventrals equidistant 



from tip of snout and last anal ray, or nearer the latter; a median series of scales from the 



dorsal to the occipital process. 



d. A caudal spot; a large faint vertically crescentic humeral spot; mouth minute; preventral 



area flat; head 4; depth 2-2.2. 



e. A. 33-35; scales 7-35 to 37-5; anal margin nearly straight; maxillary short, its length 



equals length of snout; premaxillary teeth three- or five-pointed; maxillary without 



teeth; five graduated teeth on each side of the lower jaw; second suborbital leaving 



but a narrow naked area; maxillary 4 in head; mandible 3 3. jamesi Eigenmann. 



ee. A. 31; scales 7-36-6; maxillary with a single tooth; premaxillary teeth four or five 

 pointed; four graduated teeth on each side of the lower jaw; maxillary less than snout 

 in length, 5 in head; mandible 3 in head; second suborbital but two thirds the width 



of the cheek 4. justae Eigenmann. 



dd. No caudal spot; a well-defined longitudinally ovate or round humeral spot; preventral area 



rounded; mouth large; fins large. 



/. Maxillary with many teeth; eye large, 2-2.5 in the head, the profile much depressed 



over the eye; interorbital less than diameter of eye; one fourth of the cheek naked; 



humeral spot elongate, beginning over the second scale of the lateral line; depth 



2.1-2.6; head about 4; A. 34-37; scales 7 or 8-34 to 37-6 or 7; highest dorsal ray 



not reaching adipose 5. doceana (Steindachner). 



ff. Maxillary with 1 or 2 teeth, equal to the distance from tip of snout to pupil; eye 2.5 



