8 MEMOIRS OF THE CARNEGIE MUSEUM. 



and multicuspid, it may be observed that the conic tooth may be a simple cone, but 

 is much more likely to be recurved. All the teeth of Grundulus are of this type. 

 Part of the teeth on the maxillaries of the genera with tricuspid teeth are also uni- 

 cuspid, and probably by degeneration some of those on the premaxillary. The 

 tricuspid type varies from a slender conic tooth with a minute notch on each side 

 to a tooth in which the three points are of about equal size, nearly coterminous, and 

 arranged in a line, to a heavy tooth with a blunt central point and two minute 

 lateral points, so arranged that the three points mark the angles of a triangle 

 (Probolodus) . The five- to nine-pointed teeth may have a large central cusp and 

 two graduate cusps on the sides of the tooth,the line connecting the five (or more 

 points) forming parts of an ellipse, or the points may be of nearly equal value and 

 nearly coterminous. Between these there are many shades, several variations 

 not infequently occurring in different parts of the same jaw. A very distinct type 

 of tooth as well as arrangement is found in the lower jaw of Aphyocheirodon. The 

 teeth in this jaw are usually five-pointed. The three middle points are of about 

 equal size and subtruncate, so that their tips form chisels rather than points. 

 The outer cusps are very minute and so far withdrawn from the level of the rest 

 that they are easily overlooked. That this surprising shape is not the result of 

 wear is shown by the relay-teeth which have the same shape as the rest. With all 

 these modifications the sides of the multicuspid teeth may be parallel or very 

 much contracted basally. The teeth are usually quite flat, or rather thin, but in 

 Mixobrycon the teeth are heavy and approach the shape of the teeth of the Tetra- 

 gonopterinse. In all but one species the teeth are strictly uniserial. In Megalam- 

 phodus micropterus one of the teeth of the premaxillary is sometimes out of line 

 with the rest, a little further forward, and forms either an incipient or a reminiscent 

 anterior series. 



The number of teeth as well as the shape of the teeth described above indicate 

 that the dentition of this group of the Characins is highly speciahzed. In this 

 character of high specialization they are not unique among the Characins, for it is 

 in the shape, number, and arrangement of the teeth that the greatest divergence 

 has taken place. 



The number of teeth on the premaxillary and the frequency of the appear- 

 ance of any given number is indicated in the following table: 



Number of teeth in premaxillary: 3, 4, 5 , 6 , 7 , 8, 9, 10, 11, 12, IS, 14 



Number of species having the given number of teeth: 171110 14 96 5 2 2 1 2 



In this table seventeen species occur in more than one count; to be exact, five 

 species occur in two counts, ten in three, one in four, and one in five. In other 



