of the Characinoid Oenua Piabuca. 



241 



instead of only two. In an allied species, Peteraius Leopold i- 

 anusy these lour teeth are but slightly displaced from the 

 general series, to the teeth of which they approximate more 

 closely in size and structure. Clearly, we may infer, in the 

 case ot Petersius UiUjendorJi, that the outer series has arisen 

 by extrusion from the older main series, and it seems reason- 

 able to infer a similar origin for the supernumerary teeth to 

 which I seek to draw attention in Piabuca. But, however 

 this may be, the upper teeth of Piabuca must be described as 

 forming two series. The condition is shown in fig. I. 



Teeth of Piabuca aryeittina (enlarged). 



Hg. 1 sl.ows the supernumerary preniaxillar)' teeth, forming an outer 



Bi'ries. 

 Fig. 2 shows the existence of two teeth in the maxilla. 



The figures are outlined from photographs made for me by Mr. J. Green. 



Miiller and Troschel * figure the mouth of Piabuca argen- 

 tina without giving any indication of these supernumerary 

 teeth. Moreover, in their classification of the Characinidse 

 they refer the genus to a group characterized by the possession 

 of teeth in a single series. No other original figure of the 

 teeth of Piabuca, I believe, exists ; but the figure referred to 



♦ ' Ilor,TB Ichthyologicffl. Beschreibung und AbbilJung neuer Fisclie. 

 Characiniden.' Berlin, 1845. 



