126 silurid^;. 



Blackish : lower parts whitish ; dorsal fin with a very indistinct lighter 

 longitudinal band. 

 Lake of Nicaragua. 



a. Eight and a half inches long. Presented by Captain J. M. Dow. 



21. Pimelodus petenensis. 

 D. 1/6. A. 11. P. 1/9. 



Head covered with thin skin above. The adipose fin is rather low, 

 especially anteriorly, but long, its length being somewhat more than 

 one-third of the total (without caudal) ; it is as distant from the 

 caudal as from the dorsal, its distance from those fins being less than 

 the length of the base of the dorsal. The maxillary barbels extend 

 to the origin of the adipose fin, the outer ones of the mandible nearly 

 to the middle of the pectoral. 



The height of the body is one-sixth of the total length (without 

 caudal), the length of the head two-ninths ; the head is depressed 

 and rather broad, its greatest width being three-fourths of its length ; 

 the diameter of the eye is one-half of the extent of the spout (which 

 is somewhat more than the width of the interorbital space), and two- 

 fifths of the postorbital part of the head. Tail rather deep, its least 

 depth being more than one-half of the length of the head. The lower 

 jaw is scarcely shorter than the upper ; the band of intermaxillary 

 teeth is six times as broad as long. Dorsal fin with the spine very 

 feeble, as high as long. The length of the pectoral equals that of 

 the head without snout ; the length of its spine is a little less than 

 one-half of that of the head. A minute porus mucosus in the axil. 

 Ventral fin shorter than pectoral. The length of the base of the anal 

 is somewhat less than that of the dorsal ; its posterior rays extend 

 nearly to the end of the adipose fin if laid backwards. Greyish 

 brown, with a darker band along the lateral line ; dorsal fin with a 

 light longitudinal band. 



Lake Peten. 



a. Nine inches long. From the Collection of Messrs. Salvin and 

 Godman. 



$. The adipose fin ia less than one-third of the total length (without 



caudal). 



aa. The tail above the anal fin is almost as high as the trunk. 



22. Pimelodus hypselurus. 

 D. 1/6. A. 13. P. 1/9. 



Head covered with soft skin above ; occipital process rather short, 

 triangular. Adipose fin long, one-fourth of the total length (with- 

 out caudal) ; its distance from the dorsal is two-thirds of its own 

 length. The maxillary barbels extend to the end of the dorsal, the 

 o\iter ones of the mandible to the root of the pectoral. 



The height of the body below the dorsal equals the height of the 

 tail above the anal, and is one-sixth of the total length (without 



