SOUTH AMERICAN CHARACID FISHES — WEITZMAN 143 



the more normal characid shape and is of a thinner, lighter bone than 

 the thick anterior region. The two regions are separated by a deep 

 median groove and are joined by a latero ventral connecting sheet of 

 bone. The complicated series of locking bony convolutions present 

 at the symphysis of most characids is absent. The posterior portion 

 of the dentary carries the tube for the laterosensory canal. 



The articular lies against the medial posterior surface of the dentary 

 and bears a socket for the articular head of the quadrate. The 

 angular is a well-developed bone ventral and internal to the lower 

 posterior region of the articular and dentary. 



The coronomecklian (sesamoidarticular) is a prominent bone on 

 the inside surface of the articular above the posterior region of Meckel's 

 cartilage. 



The lower jaw in the Pyrrhulinina is similar in general form and 

 shape to that of Brycon. The lower jaw of males of the genus Copella 

 is somewhat modified and this is correlated with the differences 

 found in the dentition and shape of the upper jaws (Myers, 1956a, 

 p. 12). There are two rows of conical teeth on the dentary, an outer 

 larger row and an inner row placed on a ridge of bone behind the 

 replacement teeth of the outer row. There is a slight notch along 

 the lower border of the dentary just posterior to the convoluted 

 symphysis. This notch is probably homologous with the deep 

 ventral groove in the dentary of the Nannostomina. The rest of 

 the bones comprising the mandible in the Pyrrhulinina are similar 

 in their basic relationships to those of the Characinae. 



In general shape the mandible in members of the Lebiasinini is 

 like that of the Pyrrhulinina; however, the teeth in the outer row 

 are tricuspid and similar in form to those found in the Nannostomina. 

 The inner row is a series of very small conical teeth that, as in the 

 subtribes Nannostomina and Pyrrhulinina, pass onto the lateral upper 

 edge of the jaw behind the first large row of teeth. 



The lower jaw in the Erythrininae is not unlike that in the Lebia- 

 sinini. In general, the placement of the dentary teeth in these two 

 groups is much alike; however, in the Erythrininae the second row 

 of teeth is restricted to the upper posterior edge of the dentary and 

 to the area posterior to the first row of teeth. This second row does 

 not advance forward on the crest of the bone behind the replacement 

 teeth of the first and largest row of conical teeth. 



Mandibular and palatine arches (figs. 4, 6, 7). — Regan (1911, p. 

 21) stated that Nannostomus and Characidium belong to the family 

 Hemiodontidae and that these two genera could be distinguished 

 from other hemiodontids by the possession of a single series of teeth 

 in both jaws and a broad two-headed hyomandibular. As shown 

 above, members of the Nannostomina have two rows of teeth in the 



728-42ft— 64 2 



