128 



SILTTRIDJ!;. 



The maxillary barbels extend to the ventral, the outer ones of the 

 mandible to the root of the pectoral. The depth of the tail is but 

 little less than that of the bod}'. The length of the head is contained 

 five times and a half in the total (with the caudal). The lower jaw 

 is the shorter. The eyes are situated somewhat before the middle of 

 the head, and their diameter is two-fifths of the width of the inter- 

 orbital space. Pectoral spine only half as long as the rays. Caudal 

 fin subti'uncated. (Kne)-.) 

 Mexico. 



bb. Tail gradually becoming lower from its commencement. 



25. Pimelodus pati. 



Pimelodus pati, Valenc, in d'Orb. Voi/. Amer. Merid. Poiss. pi. 1. figs. 

 7-9; C'Kr. i^- Val. xv. p. 176; Kner, Sitzgsber. Acad. Wiss. Wien, xxvi. 

 p. 416. 



B. 9. D. 1/6. A. 12. P. 1/12. 



Snout produced and depressed. Head covered with thin skiu 

 above ; occipital process five or six times as long as broad, not 

 reaching the basal bone of the dorsal spine. Adipose fin very low, 

 its length being more than one-fourth of the total (with the caudal). 

 The maxillary barbels extend on to the anal fin, the outer ones of 

 the mandible to the tip of the pectoral. The diameter of the eye is 

 one-fourth of the width of the interorbital space. Dorsal spine 

 feeble, about as long as that of the pectoral fin, and as high as the 

 bodj\ Caudal forked. Yellowish, with numerous smaU, rounded, 

 blackish spots. ( Val.) 



Eio de la Plata, Rio Branco. 



26. Pimelodus jenynsii. 

 Pimelodus gracilis, Jenyiis, Toy. Beayle, Fishes, p. 110 (not Valenc). 

 D. 1/6. A. 14-15. P. 1/9. 



Helmet smooth and not very conspicuous ; occipital process lan- 

 ceolate, three times as long as broad, not extending on to the basal 

 bone of the dorsal spine. The space between the dorsal and the 

 adipose fin a little exceeds the length of the former, the adipose 

 being twice the length of that fin. The maxillaiy barbels extend to 

 the origin of the adipose fin, the outer ones of the mandible beyond 

 the root of the pectoral. 



The height of the body is contained seven times and a half in the 

 total length (with the caudal), the length of the head six times. The 

 diameter of the eye is contained four times and a half in the length 

 of the head, and once and a quarter in the width of the interorbital 

 space. The pectorals are rather shorter than the head, and their 

 spine is strongly serrated and very little shorter than the soft rays. 

 Dorsal fin one-third higher than long, with the spine slender. Caudal 

 forked, with the upper lobe a little longer than the lower. A dark 

 band along the lateral line. {Jen.) 



Rio de Janeiro. 



