DRIVER— THE LUCIOPIMELODIN^. 451 



The two lobes of the air-bladder are very small. In a fish 200 

 mm. long they are 2.5 mm. in diameter and the distance between the 

 outer margins of the two capsules measures 12 mm. They are pear- 

 snaped, tapering to a small canal connecting the two capsules. 



Liiciopimelodiis and Megaloncma are certainly closely related to 

 Perugia. This becomes quite evident when we examine the air-, 

 bladder and the anterior vertebrae associated with it. An examination 

 of these structures also demonstrates that Luciopimclodus and 

 Megalonema are not related to the Pimelodinas with which they have 

 been associated. 



The air-bladders in these two genera are not indirect contact with 

 the skin. They extend outward to near the skin, being separated 

 from it by a thin layer of fat. 



As in the structure of the air-bladder and the Weberian apparatus 

 Perugia, Luciopimelodus and Megaloncma differ greatly from all 

 the genera of the Pimelodince, they may well be separated into a new 

 subfamily, the Luciopimclodincv. 



Text-Fig. 2. Megaloncma platanum Giinther. Photograph by Sur. Valette, 

 Jefe de la Oficina Fomento de Pesca. Buenos Aires. 



In Cuvier and Valenciennes, "Hist. Nat. Poissons," XV, 1840, 

 p. 176, Valenciennes described a new species which he called Pime- 

 lodus pati basing his description on a specimen 30 inches long col- 

 lected by d'Orbigny, a very small specimen which he received from 

 the museum at Lisbon, and on a drawing in the MS. of Father Feuil- 

 lee, in Hugard's library. Later in d'Orbigny's " Voyage dans I'Amer- 

 ique Meridionale," V, 2c Partie ; Poissons, 1847, P- 7. plate I., Fig. 

 7-9, Valenciennes figured the species. 



