134 SILUKIDiE. 



thirds in the total. The band of teeth in the upper jaw is of mode- 

 rate breadth, without prolonged lateral portion. The basal bone of 

 the dorsal spine is narrow, about as long as the occipital process. 

 The maxillary barbel extends to the end of the head. Pectoral spine 

 very stout, depressed, serrated along both edges. Caudal rounded. 

 Brown, marbled with darker ; a series of white spots along the base 

 of the dorsal and anal fins ; dorsal, adipose, and anal fins blackish 

 brown, with a white margin ; caudal with brown dots, and with a 

 blackish band edged with white pos'teriorly, across the margin ; the 

 pectorals and ventrals blackish brown 

 Brazil; Guiana. 



a. Fine specimen, 4 inches long. From the Collection of the Zoo- 

 logical Society. 

 b-c. Fine specimens. Fssequibo. From Mr. Ehrhardt's Collection. 



41. Pimelodus mangurua. 



Pimelodus mangurus, Valenc. in d'Orb. Voy.Amer. Merid. Poiss. pi. 1. 

 figs. 4-6 ; Cuv. $ Vol. xv. p.' 156. 



B. 9. D. 1/7. A. 9 (?). P. ^. 



Head broader than long, its length being one-fifth of the total ; 

 lower jaw rather the longer. The maxillary barbels extend scarcely 

 to the praeoperculum. Light brown, dorsal and caudal fins darker. 

 (Vol.) 



La Plata River. 



E. The occipital process is short ; body moderatelv elongate ; adipose 

 fin not longer than dorsal. 



42. Pimelodus platychir. 



D. 7. A. 8. P. 10. V. 6. 



Head and anterior part of the body much depressed;, head rather 

 longer than broad, its length being contained four times and a third 

 in the total (without caudal), the height of the body one-seventh. 

 The posterior part of the trunk is subcylindrical, the tail compressed ; 

 the least depth of the latter is less than that of the body. Head 

 entirely covered with soft skin ; eyes very small, partly directed 

 upwards, placed a little nearer to the end of the operculum than to 

 that of the snout. The width of the interorbital space is less than 

 the extent of the snout, which is rounded. Nostrils on the upper 

 side of the snout, the anterior rather remote from the posterior. 

 Gleft of the mouth of moderate width, each jaw with a band of 

 villiform teeth ; the upper is somewhat longer than the lower. The 

 maxillary barbels extend to the end of the head ; the outer mandi- 

 bulary barbels are at the angle of the mouth, extending to the base 

 of the pectoral ; the inner mandibulary barbels are shorter, and placed 

 immediately behind the margin of the lower lip. Gill-openings 

 wide, the gill-membranes not attached to the isthmus, and only 



