G. Hemiodontinae.—Partially herbivorous; dentition imperfect; maxillary well developed; scales cycloid. American: Hemiodus, Caenotropis, Saccodon, Parodon.
H. Distichodontinae.—Entirely or partially herbivorous; teeth small but well developed; maxillary well developed; scales ciliated. African: Nannaethiops, Neolebias, Distichodus, Nannocharax, Xenocharax.
I. Citharininae.—Herbivorous; teeth minute or absent; maxillary small; scales cycloid or ciliated. African: Citharinus, Citharidium. American: Prochilodus, Curimatus.
Fig. 348.—Distribution of the Characinidae.
The genera in the above sub-families are mostly founded on the dentition and the extent of the praemaxillary and maxillary bones, which are astonishingly varied, as may be seen from the annexed figures showing the open mouths of a few of the most remarkable types. As I have already pointed out, the character often given as diagnostic of this family, viz. the maxillary forming part of the oral border, is not absolutely constant; this bone is often much reduced, and it is entirely excluded from the mouth in Ichthyoborus and Neoborus. The branchiostegal rays number 3 to 5 only. The fins never bear pungent spines, and the ventrals have 6 to 13 rays. Barbels are absent. In most of the herbivorous forms the brain-case is produced forward to the nasal capsule, whilst in most of the carnivorous forms they are separated by an interorbital septum; but there are exceptions to this correlation, and as otherwise closely related genera may differ in this respect, I have not been able to make use of the character in defining sub-families.
Fig. 349.—Open mouths of Characinidae. (After Müller and Troschel.) A, Macrodon trahira; B, Piabucina argentina; C, Brycon falcatus; D, Chalceus angulatus; E, Serrasalmo rhombeus; F, Distichodus niloticus.
The air-bladder is divided into an anterior and a posterior part by a constriction; the posterior part is the longer, and its anterior portion is cellular in Erythrinus and Lebiasina. Pyloric appendages to the stomach, which are constantly absent in the Cyprinids, are more or less numerous. An accessory respiratory organ in a diverticulum above the fourth branchial arch has been observed in Xenocharax and Citharinus.
