138 Annals of the Carnegie Museuim. 



(With 281), Rio Paraguay, at Ascuncion ; four specimens from 

 Villa Rica (part 470). 



67. Astyanax iheringi (Boulenger). 



Seventeen specimens (455, 456), from mountain streams of Sapucay. 



68. Mcsnkhausia dichrourus (Kner). (Plate XLL, Fig. 1). 



A single beautiful specimen 57 mm. long (299) from the Rio Para- 

 guay at Tuyuyu, Matto Grosso, probably belongs to this species. The 

 proportion and measurements differ somewhat, and are as follows : D. 

 9; A. 26; depth 3.5 (the type has depth 2^) ; head 4.5; scales 5- 

 35-3. Maxillary without teeth, much curved. Middle caudal rays 

 and the tips of all the rays dusky or black, the tips of the lobes beyond 

 the scales black. A well-defined lateral band extending from caudal 

 to below front of dorsal where it is rapidly contracted and tends to 

 disappear before reaching the faint humeral spot. 



A low adipose ridge extending from the adipose fin half way to the 

 dorsal. We have other specimens from Corumba and Asuncion. 



69. Moenkhausia agassizi (Steindachner) (Plate XL1, Fig. 2). 



Two small specimens Nos. 10164, 4° mm - an d 10165, 33 mm. from 

 Corumba (305) agree very closely with this species but differ in 

 having the lateral line incomplete. If this is a constant character and 

 not the condition of the age of the specimens, these specimens must 

 be held as species distinct from agassizi. Until further specimens are 

 available this question may be left in abeyance. 



The great similarity of the specimens with a complete lateral line 

 and an incomplete one is in itself not proof that the two sets of speci- 

 mens belong to the same species. There are remarkable cases of 

 parallelism between other species concerning whose generic difference 

 there cannot be the slightest doubt. 



Head 3.5 ; depth 2.5 ; D. 10 ; A. 23 ; scales 5-24-3^ ; pores on 

 7 or 8 scales. 



Maxillary without teeth; eye 2.5 in the head; snout 4^ ; body 

 deep, robust but moderately compressed ; dorsal and ventral outlines 

 equal ; caudal peduncle short and deep. 



Dorsal behind ventrals, the highest ray about equal to the length of 

 the head ; caudal lobes about iy£ times as long as the middle rays ; 

 highest anal ray about twice the height of the lowest, the fin not dis- 

 tinctly falcate ; ventrals reaching the anal ; pectorals reaching beyond 

 origin of ventrals. 



Top of head and tip of lower jaw minutely but densely punctate ; large 



