380 



Annals of the Carnegie Museum. 



one II and the other 9.5 cm. long, with the upper jaw, as in the other 

 examples, slightly protruding; inner edge of caudal lobes dusky and 

 lower lobe with a dusky band in its middle; outer half of dorsal dusky, 

 with small pigment dots, while its basal half is white; ventral side 

 silvery white. 



No. 286oa-b, cotypes, 9.5 and 14 cm.; rather slender, resembling 

 the type in shape, etc., but more spotted and the spots almost extend- 

 ing to the ventral side. 



This species is distinguished from P. clarias by fewer gill-rakers 

 on the lower branch of the first gill-arch, having 5-24, 4-14, 6-17, 

 6-13, 5-15 and 5-15. It has evidently been derived from P. clarias, 

 which has in some way found a habitat above the Iguassu Falls, where 

 it is well separated from the present parent form below the falls. 

 Pimelodus clarias is not found anywhere in the swampy headwater 

 streams coming from the Brazilian table-land. I think it may have 

 been deposited above the fall by water-birds, especially those known 

 by the natives as "biguas," or by the Indians themselves. 



I take great pleasure in dedicating this species to Dr. A. E. Ortmann. 



Genus Pygidium Meyen. 

 5. Pygidium davisi, sp. nov. (Plate LXXVII.) 



Type, No. 2862, Serrinha Parana, Dec. 23, 1908. 



D. 7 + a stay; A. 5, and a stay or rudimentary ray; V. 5, and only 

 one-half the length of the anal; head 5.5 in length and heart-shaped; 



Fig. I. Pygidium davisi. Dorsal view of head. 



body slender, and the anterior part round, its greatest depth 8 to 9 

 in the length to base of its caudal; part back of the dorsal fin much 



