28 



INDIANA UNIVERSITY 



In some species of these genera or some individuals of one 

 species the teeth are crowded and some are moved forward out 

 of line to form an anterior series on the premaxillary. In Coelu- 

 richthys, the teeth are still in a single series in some specimens, 

 and in a double series in othersi. In some species of Chalcinus, the 

 teeth are in a single series, and in others they are in two. 



In a few cases the double series of teeth has given rise to three 

 series. By such a change Creatochanes has given rise to Bryconops 

 and Bryconamericus has given rise to Creagrutus and Piabina. 

 Half way conditions are found in a host of species where the front 

 series of the premaxillary teeth are not in line, alternate teeth, 

 roughly speaking, having been withdrawn from the front series 

 to form an incipient middle series. 



In some cases the number of rows of teeth is being diminished. 



In Piabucus dentatiis, in fa,ct, in the Piabucininge in general, 

 the anterior series of premaxillary teeth has been reduced to a 

 single small tooth on each side. In Piahucies melanostomus of 

 Paraguay, closely related to demtatus of the Amazon, even this 

 small tooth of the anterior series has disappeared. In the Rhoad- 

 sinae, the anterior series of teeth does not make its appearance 

 until very late in life, and then the teeth are insignificant. In 

 (Jeratobranchia and Henochilus, it is the inner series of teeth 

 that is disappearing, and in Psalidodon the inner series is gone. 



Additional series of teeth appear by the crowding out of teeth 

 from a single series, shall we say through an overplus of tooth- 

 developing power. Series of teeth do not disappear by being 

 absor]>ed into other series but hy the dwindling of the teeth, shall 

 we say by the diminution of the tooth-developing power. 



An odd condition in the arrangement of the teeth in the lower 

 jaw has apparently arisen independently in Moenkhausia, Stich- 

 ono'don, and Fowlerina. In each of these genera some one, or 

 more, species has the second tooth of the lower jaw moved for- 

 ward out of line with the rest. 



Finally, the adipose fin, one of the characteristic features of 

 the Characins, has disappeared a number of times. By the loss 

 of the adipose: 



ITyphessobrycou lias siveii rise to ITasemania : 

 lialmciiia lias siven rise to Lebiasiiia : 



(JastcrdiK'lccns lias .iiiveii rise to Carnesiella ; 

 ? lias sivcii rise to Stevardia ; 



•? has si veil rise to Xeiiiatobrycnii. 



Among a large number of specimens of Lebiasina, recently 



