410 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [68] 



This species is one of the most common food-fishes of our southern 

 coast, being an excellent pan-fish. Notwithstanding the numerous 

 nominal species which authors have recognized, there is no evidence 

 whatever of the existence of more than one species of Leiostomus on 

 our coasts. 



The name xanthurus is an unfortunate one, as in this species the 

 caudal fin is never yellow. This name came about through confusion 

 with Bairdiella chrysura, in which species the caudal fin is bright yel- 

 low. 



Genus XV.— PACHYUEUS. 



Pachyurus Agassiz, Spix Pisces Brasiliens., 1829,123 (squamipennis). 

 Lepipterus Cuvier & Valenciennes, Histoire Naturelle des Poissons, v, 151, 1830 

 (francisci). 



Type : Pachyurus squamipennis Agassiz. 



This genus is composed of fresh-water Scirenoids inhabiting the rivers 

 of Brazil. It is well separated from Scicena (Ophioscion) by the weak 

 dentition. Two groups or subgenera are readily distinguished by the 

 form of the mouth, the group called Lepipterus agreeing in this respect 

 very closely with the species called Pacliypops, from which Lepipterus can 

 only be separated by the absence of the small barbels at the chin, which 

 are usually present in the species of Pacliypops. As these barbels are 

 quite small, and in individuals even occasionally absent, Dr. Steiudach- 

 ner has proposed to unite Pacliypops with Lepipterus as a subgenus under 

 Pachyurus. There is no doubt that Pacliypops. Lepipterus, and Pachy- 

 urus together constitute a single natural group. The characters drawn 

 from the form of the mouth and of the preorbital are subject to inter- 

 gradation. Unless the presence of the barbel can here, as elsewhere, be 

 used as a mark of generic distinction, all the species must be placed in 

 Pachyurus. It seems to us, however, that convenience is but served by 

 placing all the species in which barbels are habitually developed in one 

 genus (Pacliypops), and those which never have them in another (Pachy- 

 urus). 



ANALYSIS OF SPECIES OF PACHYURUS. 



«. Mouth terminal, oblique, small, but larger than in other species ; the maxillary- 

 reaching front of pupil, its leugth about 2| in head ; jaws subequal ; caudal 

 fin densely covered with scales, so that it is thick to the touch ; preorbital 

 scarcely turgid (Pachyurus). 

 b. Body compressed; the back elevated, the nape especially compressed; head low 

 and narrow ; profile depressed above the eyes, so that the sharp, projecting 

 snout leaves a considerable concavity in the line of the profile; teeth in 

 broad bands, all equally minute in both jaws; preorbital broad, broader 

 than eye ; skull not specially cavernous ; pores and slits on snout obsolete ; 

 preopercle sharply but rather finely serrate on tine bony border ; eye large, 

 5% in head; snout 3|; interorbital width 5£ ; gill-rakers almost obsolete, 

 2 + 4 in number, not higher than wide; pseudobranchire small; caudal fin 

 rhombic, much thickened ; soft dorsal scaly, but not thickened ; longest 



