. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. EcuADOREAx Glaxdulocaudine Fishes • Roberts 499 pterotic parietal supraoccipitai. exoccipital parasphenoid prootic intercalar Figure 8. Phenacobrycon henni. Lateral view of cranium ( specimen). basioccipital lotabrycoii hooks occur on all of the pelvic rays but are medially directed and re- stricted to the inner edge of each ray (Fig. 4). In Phenacobrycon and Landonia the outermost pelvic ray has no hooks. In Landonia the hooks are medially directed and restricted to the inner edge of each ray as in lotabrycon,
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. EcuADOREAx Glaxdulocaudine Fishes • Roberts 499 pterotic parietal supraoccipitai. exoccipital parasphenoid prootic intercalar Figure 8. Phenacobrycon henni. Lateral view of cranium ( specimen). basioccipital lotabrycoii hooks occur on all of the pelvic rays but are medially directed and re- stricted to the inner edge of each ray (Fig. 4). In Phenacobrycon and Landonia the outermost pelvic ray has no hooks. In Landonia the hooks are medially directed and restricted to the inner edge of each ray as in lotabrycon, but in Phenacobrycon the hooks are dorsally directed and occur on all branches of each ray, iis in Brycon- (imericus scJeroparius. Replacenwnf iecth and tooth rcpJacc- nient. In lotabrycon, as in other minute characins with conical teeth, the replace- ment teeth are in varying stages of de- \'elopment. In adults of Phenacobrycon and Landonia, as in other characids with multicuspid teeth, all of the replacement teeth on one side of both the upper and lower jaws are always in the same stage of fonnation, and at least in Phenacobrycon all the teeth on one side of the jaws are probably replaced in one continuous process; in other words there is nearly simultaneous replacement of one-half of the entire dentition, first on one side, then on the other side of the jaws, as occurs in Brycon and other characids with multi- cuspid teeth (Roberts, 1967). In a popu- lation sample of 97 Phenacobrycon (MCZ 48660) are 85 specimens in which all of the teeth are in functional position on both sides of the jaws, and 12 specimens in which the teeth on only one side of the jaws are in the process of replacement. In lotabrycon the replacement teeth in both jaws lie in the gum just inside the row of functional teeth. In Phenacobrycon the replacement teeth for the internal row of teeth on the premaxillary and for the single small tooth on the maxillary lie simply in the gum (Fig. 5), but the replac
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