Petersen, New Ephemeridae from Denmark, Norway, Argentine. 553 



bad condition. Other specimens, dried and damaged, are labelled 

 Pedregal, 29. X. 1906. 



3. Genus n v. 

 With only a single subimago available for study, it is not 

 possible to define this genus or describe the species. Reference 

 to E a t n ' s Analysis 

 of the Classification of 

 the Ephemeridae in Trans. 

 Lin. Soc. London, series 

 2, zool., vol. 111, pag. 

 309 , is favourable to 

 its being classed with 

 Hagenulus a genus of the 

 LeptophleUa Type, from 

 which it differs in the 

 more roundly arched 

 Anal nervures and more 

 boldly rounded anal- 

 axillar margin of the 

 fore wings — features 

 which are paralleled in 

 some members of the 

 2-winged Caenis Type. 

 Subimago (dried). 

 cf. Mesothorax above 

 greyish. Abdomen above 

 light greyish, the two ^^^- ^- ^^"^^ ^°^ ^i^<^ ^i^S («' ^) »f sub- 



first Segments brown ; ^"'^^^ ^^^ ^'■"™ ^^^T' ^' ^'''''' ''' ^'""^ 

 ö ' wmg, enlarged. 



abdomen ventral ly whi- 

 tish. Legs very pale; 

 the anterior femora 

 marked with brownish 

 stripes. Fore wings hya- 

 line with a greyish tint. 

 Costa, radius and espe- 

 cially subcosta dark 

 greyish ; the other of longitudinal nervures only a little darker 

 than the membrane. The transversal nervures only visible in 

 transparent light. Three setae, which are whitish with jet black 

 annulations. Hind wings present and very remarkable by their 

 long tail like projection from the anterior margin. Membrane 

 with 3 or 4 longitudinal nervures. 



Long. 5 mm ; wing 6 mm ; setae 14 mm. 



Fig. 6. Hind tarsus of subimago (o^) from 

 Chacras de Coria. 



