102 Annals of the Carnegie Museum. 



covering the whole scale, meeting at approximately right angles 

 in the middle of the apical field; apical margin very faintly inclined 

 to be crenulate; basal folds quite strong; radii apical, very strong, 

 very variable, about 4 to 10, the arrangement fan-like, the outer 

 ones often curved. A very distinct type of scale, much less like 

 that of A. polylepis than the latter is like DeiUerodon. 



Astyanax potaroensis Eigenmann. Small transversely suboval scales 

 with the nucleus subbasal and the radii few; the nucleus is reticulate 

 as in A. polylepis, and the radial area is covered with widely spaced, 

 largely broken circuli, which meet in the middle line at less than a 

 right angle. This is of the general type of A. polylepis and a&ra- 

 moides. 



Astyanax mucronatus Eigenmann. Small broad scales, with nearly 

 the outline of a half circle; obtuse laterobasal angles; basal and 

 lateral circuli, the latter widely spaced; nuclear area minutely 

 squamose; radii usually reduced to two, which are distinct; no circuli 

 in apical field, and the last of the lateral circuli strongly oblique 

 (directed to the margin). This is strikingly different from the 

 other species of Pcecilurichthys, and approaches the condition of 

 Cheirodon quite closely. (Superficially, the fish is much like 

 Cheirodon.) 



2. Astyanax s. str. 



Astyanax mutator Eigenmann. Small scales, quite of the A. polylepis 

 type, the radii about six, the radial field wholly without circuli; 

 lateral circuli widely spaced, the innermost longitudinal, or some 

 even bending over mesad; nuclear region simple, not reticulate. 



Astyanax guianensis Eigenmann. Scales thin, much broader than 

 ong, exactly as in A. mucronatus, except that the two especially 

 strong radii are usually more divergent, so that if continued basally 

 to the nucleus they would form a V. The nuclear area has a sort of 

 honeycomb-like reticulation. The fishes mucronatus and guianensis 

 are much alike. 



Astyanax essequibensis Eigenmann. Broad thin scales, inclined to be 

 triangular; characters in general as in mucronatus, but radii weaker 

 and more irregular. The widely spaced lateral circuli are oblique, 

 directed toward the margin; there are no circuli in the radial or 

 apical field; nuclear area not ret'culated, all that is left of the 

 reticulation being a few irregular markings. 

 According to the scales, the species of Astyanax would be classified 



thus: 



