Petersen, New and little-known species of Epbemerida fr. Argentine. 341 



species diifer considerably from the type, and I thiiik this larva 

 belongs to that group. The forehead is very broad , and the 

 body is broad and , in some degree , flattened as in Ecdyiirus. 

 The fore femora very broad. The apical Joint of the labial palpi 

 very short, and the mandible has only one blunt tooth. Thorax 

 and abdomen light brown. Fore femora with a small dark brown 

 band in the middle , fore tibia with two dark brown bands , a 



Fig. 12. Larva of Thraulus. 



a Labium, h left maxilla, c left mandible (all seen from underside), 



d left mandible, seen from above. 



broad one near to the base and a smaller and darker one at the 

 apex. Setae yellowish brown with small dark brown annulations 

 at the base. 7 pairs of double gills ; the 7*^ pair the smallest. 

 The hind angles of 8'^ and 9'^ segments prolonged into sharp 

 lateral spines. 



Length 8 mm ; setae 9 mm. 



10. Larva of Baetis. 

 Some few larvae of the common Baetis - type were found 

 amongst the material , and 4 of them were fullgrown. As there 

 are not yet described larvae of this genus from Argentine, I give 

 some figures of the mouthparts and of a gill to show the likeness 

 to our European forms. The only thing I know about South 



