142 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lie 



mandible as it does in the Characinae, Pyrrhulinini, Lebiasinini, and 

 Erythrininae, but it is limited in its anterior extent to an area under 

 the long, slender, lower, posterior process of the quadrate. The 

 opercle and subopercle are similar in Lebiasininae and Erythrininae 

 and are not markedly different from those of the Characinae. 



Upper jaw (figs. 6, 7). — The premaxillaries of the Nannostomina 

 bear a single row of one to seven small cuspid teeth. A row of "re- 

 placement" teeth is present behind the main outer row. The pre- 

 maxillary is not divided into upper and lower processes but is more or 

 less lenticular in its horizontal outline. Its dorsal surface has a de- 

 pression to receive a lateral process of the ethmoid bone. 



The maxillaries of all members of the Nannostomina are essentially 

 alike. The maxillary has a single tooth with from one to six cusps. 

 The maxillary is a flat lamella of bone with a robust, conic upper 

 process extending toward the anterior part of the ethmoid. Pos- 

 teriorly the maxillary does not reach the second infraorbital. 



The premaxillary of the Pyrrhulinina bears one to two rows of 

 simple conic teeth while the maxillary has a single row of conic teeth 

 along its edge. The maxillary is elongate and reaches well along the 

 second infraorbital to about the third infraorbital bone. The pre- 

 maxillaries of members of the Pjrrrhulinina is not well divided into 

 upper and lower processes. 



The premaxillary in members of the Lebiasinini has a single row of 

 tricuspid teeth similar in general shape to those of the Nannostomina. 

 The premaxillary is fairly well divided into an upper process and a 

 lower lamella. The maxillary has a single row of peglike tricuspid 

 teeth along its anterior edge, and its lower limb reaches to the third 

 orbital bone. 



The premaxillary in members of the Erythrininae has well-developed 

 upper and lower limbs and a single row of conical teeth. The max- 

 illary is well developed and in Hoplias the fan-shaped distal end is 

 external to the second infraorbital. In Erythrinus and Hoplery- 

 thrinus the fan-shaped distal end of the maxillary is included under 

 the second infraorbital. In the Erythrininae the maxillary almost 

 reaches the third infraorbital. 



Lower jaw (figs. 6, 7). — The dentary of adult specimens of the 

 Nannostomina bears two rows of teeth ; the anterior large teeth of the 

 outer row have five or six cusps while the posteriormost few teeth may 

 have the number of cusps reduced from one to fom*. The second row, 

 composed of small conical teeth is on a crest of bone lying behind the 

 replacement teeth of the first row. The shape of the dentary is rather 

 remarkable and diagnostic of the Nannostomina. It is divided into 

 two regions. The anterior region bears the teeth and is approxi- 

 mately like the premaxillary in shape. The posterior portion is of 



