VISCEEAL ANATOMY OF THE CIIAEACINID.^J. 53 



sliows the stomacli of Sarcodaces contracted ; fig. 3, that of Macrodon distended ; both 

 arc represented as having been o])ened. 



The cardiac chamber is often prolonged beyond the pyloric flexure into a more or 

 less pronounced blind sac. This prolongation is large in IIijdrocyoH (fig. 1), still larger 

 in Salminns, and yet further exaggerated in Serrasalmo. It is large also in Macrodon 

 (fig. 3) and Eriithrinus, in Bryconaetliiops, and in Tetragonopterus ahramis. In 

 Sarcodaces (fig. 2), Petorsins, and at least some sjiecies o? Alesfes it is smaller. In the 

 other forms examined by me this sac can hardly be said to exist. This is most decidedly 

 the case with the herbivorous forms, the stomach and entire alimentary canal of whicli, 

 however, are altogether peculiar. The cardiac chamber is perforated near its anterior 

 end by the opening of the ductus pneumaticus, to which 1 shall refer later. I merely 

 wish at this stage to point out that in at least some cases the orifice of the duct seems 

 to be actually in the wall of the stomach, rather than the oesophagus, if one may judge 

 from the extension in front of it of the rugose folds. Such is the condition, for example, 

 in J^rijthrimts and Macrodon, in Sarcodaces, Hydrocyon, Sahninus, Ichthyohorus, and 

 many of the forms I have examined. 



In other cases, however, in which a sudden transition is apparent from oesophagus to 

 stomach, the opening of the duct appears to be just at or behind the junction of the 

 two. This I have observed in Dlstlchodus, Serrasalmo, Micralestes, EmjnatkichUtys, 

 and Xenocharax. In certain other cases — Citliarinus, Lehiasina, Alestes nurse, and 

 Leporimis — the orifice is in the narrower and thicker part of the tract, which one is 

 inclined to regard as the a-sophagus. 



The ascending jiyloric limb of the stomach is usually firmer and thicker-walled than 

 the cardiac chamber. This condition becomes greatly exaggerated in Citharimis and 

 the other herbivorous Characinidse ; so much indeed that whilst the cardiac chamber is 

 extremely thin and delicate, the pyloric limb assumes the character of a veritable 

 gizzard. The contents of the canal — vegetable matter and miul — are reduced after 

 passing through this gizzard to the condition of an extremely soft pulp. Cithariiius, 

 Distichodus, Xenocharax, Prochilodus, and Ctirimatus agree in this particular, as also 

 in others to be mentioned later. Xenocharax, however, in this as in other points 

 presents a lower stage of differentiation than the other forms just named, the difference 

 between cardiac and pyloric regions being less marked. 



In the newly discovered form Cltharidinm *, which may ho described, as regards its 

 external charactei's, as a Citharlnns with ctenoid instead of cycloid scales, I have not yet 

 had the opportunity of observing these relations. 



The Pyloric Cceca. 



The stomach is marked off from the intestine, sometimes by a slight constriction, 

 especially in Citharinoids, but also by tlie pyloric appendages, which are constantly 

 present in considerable number in the Characiuidie. 



* Boulenger, G. A., "Description of a new Characinid Fish discovered by Dr. W. J. Ansorge in Southern Nigeria." 

 Ann. & Mag. of Nat. Hist., Scr. 7, vol. ix. VJQ-J, p. 144. 



