56 Synopsis of the Fresh Water Fishes^ 



characters, whicli will distinguish it from Poecilurichthys pro- 

 per. The tail is without the large spot which is found in almost 

 every species, not only of that genus, but of almost every other 

 Characin found in South America, or its zoological dependen- 

 cies. 



This group we have provisionally only elevated to the rank 

 of a sub-genus, whicli we have called Hemigrammus,* intending 

 by that name to allude to the lateral line, which does not tra- 

 verse more than half of the length of the side. 



In the genus Poecilurichthys, most of the species which have 

 been described by Valenciennes as belonging to the second 

 section of Tetragonopterus, will be included. These are 

 Poecilurichthys Linnaei, P. taeniatus, first described by 

 Jenyns, P. grandisquamis, or Tetragonopterus grandisquamis, 

 of MM. Muller and Troschel, P. Orbignyanus, described by 

 M. Valenciennes, P. fasciatus, first described as a Chalceus by 

 M. Cuvier, P. scabripinnis, described by Jenyns, P. Peruanus, 

 a species of Muller and Troschel, and P. Wappi, first described 

 by Valenciennes. There are four other species which have 

 been referred by the great ichthyologist of France to his second 

 section, which probably do not belong to this genus. The 

 Tetragonopterus interruptus of Jenyns, which he had not seen, 

 but which was conjectured by him to be a species of his genus 

 Piabuca, hardly belongs to either that genus, as it should 

 properly be restricted, or to Schizodon of Agassiz, which was 

 united to Piabuca by Valenciennes ; by the small number 

 of anal rays, it appears to be more nearly allied to the genus 

 of Agassiz, but is probably the type of a new one, which will 

 be distinguished, among other characters, by the imperfect 

 lateral line. The Tetragonopterus viejita Val., T. melanurus 

 Val., and T. spirulus Val., are perhaps types of as many dis- 

 tinct genera. 



* 'H/ii half, and Fpamxa, line. 



