12 
ESBEN-PETERSEN. EPHEMERIDA. 
the median nervure till the point where this is forked. Abdomen above with several, 
smaller and larger, brownish spots. Venter pale greyish yellow. Autennae, legs and setae 
pale greyish yellow. The middle joints of setae dark brown on the sides. Hind angle 
of segments terminating in a long, spiny tooth. Antennae thiu and short. Setae equal in 
length; the two uttermost hairy on their inner side, the middle one on both sides. 7 pairs 
of nearly uniform trachéal gills being each apically broadly rounded and only with few 
trachéal branches. Length 13—14 mm.; setae 5 mm. 
The larva is slender and much like the Baëtis larva. A sériés of larva, in the nympheal 
stage, were present. 
1. VIII. 09 89, at the tundra of Kara; 16. VIII. 09 № 262, on the Pyderata river ; 
21 . VIII. 09 № 277 on the river Niada-jaha. 
