Note on the Characid genus Brachychalcinus Boulenger (1892), including the description of a new species

In a previous paper (1952, p. 190) I reported upon a specimen from the Lucie River, Surinam, doubtlessly belonging to Boulenger's genus Brachychalcinus, but had to abstain from giving a definite specific identification on account of the lack of comparative material, the insufficiency of previous literature, and the obviously juvenile state of the single specimen. A possibility to look once more into this matter, and to amend my previous statement, was brought about by the existence of eight specimens from the same river system, and probably belonging to the same species, in the collections of the Chicago Natural History Museum, and the offer to have these sent to me as a loan. For this courtesy, and for the loan of a single juvenile specimen of Brachychadcinus retrospina Boulenger, I am indebted to Dr. R. F. Inger, Assistant Curator of Fishes of the Chicago Natural History Museum. The genus Brachychalcinus Boulenger (1892, p. 11) belongs to the subfamily Stethaprioninae, a subfamily allied to the Tetragonopterinae but differing by the possession of a procumbent predorsal spine. Within this subfamily, however, Brachychalcinus differs from the other, and better known genera, by the shape of this procumbent spine, described by Eigenmann & Myers (1929, p. 508) as "trigger- or hammer-shaped, its free portion forming a longer anterior and shorter posterior branch, both of which are sharply pointed". It is triangular in lateral view, with the longest side about continuous with the dorsal outline, its two further sides concave, and is attached with the lower angle. A similar spine is found just before the origin of the anal fin. Of this very rare South American genus, only two species hitherto have