44 THE AMERICAN CHARACIDAE. 



The next case is that of e, the enlarged third suborbital. This character is 

 found in Knodus with a scaled caudal and in Creagrutus, Piabina, and Brycon- 

 americus with a naked caudal. The last three genera are undoubtedly closely 

 related and for the present purpose count as one. Knodus is a Bryconamericus 

 in all but its scaled caudal. We are, therefore, compelled to assume either that 

 if the ancestors of Knodus had the caudal scaled, that it has paralleled Brycon- 

 americus in the character of its cheek or that if its ancestors were identical with 

 those of the latter genus that its caudal has independently acquired scales. 



The case presented by the character d, three rows of premaxillary teeth, is 

 much simpler and clearer. This character is found in Microgenys, Creagratus, 

 Piabina, and Bryconops. It is quite certain that the latter genus has been 

 derived from an ancestor like Creatochanes and that the others have been de- 

 rived from an Astyanax-like ancestor. Microgenys, Creagratus, and Piabina, 

 on the one hand, and Bryconops on the other, have independently acquired 

 three series of teeth. In this case the steps by which this has been accomplished 

 are indicated in a variety of species of the subfamily. In many species alternate 

 teeth of the front series of the premaxillary are withdrawn from the line of the 

 rest, thus forming an incipient third series. In Moenkhausia melogramma and 

 in Bryconamericus exodon this process has almost yielded additional genera 

 with three series of teeth. The modification from one to the other condition 

 is a perfectly progressive one, without notable breaks or saltations. 



The next character c, teeth along the entire maxillary, has again been inde- 

 pendently derived from C several times. Here we have not only the evidence 

 of several distinct, not closely related, genera which have the character but 

 also the evidence from changing species. I have elsewhere called attention to 

 some specimens referred to as Aslyanas aeneus nicaraguensis. Of thirty-five 

 specimens from Lake Nicaragua, there are nine with two teeth, two with three 

 teeth, five with four teeth, five with five teeth, five with six teeth, five with seven 

 teeth, three with eight teeth and one with nine teeth in the maxillary. The 

 normal number is two. Phenacogaster is in a similar state of transition. Pris- 

 tella, Hemibrycon, Nematobrycon, Hollandichthys, and Pseudochalceus have 

 acquired complete dentition for their maxillaries in at least three independent 

 groups. 



The most interesting and conclusive evidence of the independent origin 

 of the same character in different genera is presented by the character b, the 

 incompleteness of the lateral line. Not only have we the evidence from widely 

 divergent genera with this character, but we again have species in a state of true 

 mutation. Most remarkable of all is one species of which I have been able 



