4 
ESBEN-PETERSEN. 
Of tliis rare species, wliich was described frora a single specimen iu the Linnean 
Museum in London, and afterwards was found in numbers at Aal in Norway, there is a 
pinned specimen, S, without setæ, in the collection (found at 29. VIII. 1909, on the river 
Longot-johan). 
The specimen agréés very well with the description given by Eaton. The fore legs, 
dark yellowish brown, the hind legs yellowish white. All the femora with a dark distal 
band; knees dark, and the joinings of the tarsal joints with dark annulations. The venter 
of most segments with markings as shown in Fig. 3 b. 
Fig. 3. Siphlurus Linnaeanus Eat. Ventral view. 
a Subimago, 9 , from Sweden. b Imago, O, from the river 
Longot-johan. 
Fig. 4. Siphlurus Linnaeanus Etn. Dorsal view 
of pénis and of basis of forceps. 
When I hâve given Siphlurella Thomsoni as synonomous with the species of Eaton, 
it is according to a minute examination of original description and comparison with 
a couple of specimens, S and 9 , subimagines from Smâlaud, forwarded to me by 
Dr. S. Bengtsson. 
I cannot follow S. Bengtsson in constituting a new genus on différences as to the 
proportional length of legs and tarsi within this genus. These variations, alluded to by 
Eaton (A Rev. Mon. of recent Ephem. or Mayfl. Lond. 1883—88 pag. 214), and also 
occurring, for instance, between Siphlurus aestivalis Etn. ( Siplil . spinosus Bengts.) and 
Siphluris lacustris Etn. ( Siphl . Zetter stedti Bengts.), are of great specific but of no 
generic value. Regarding the shape of the pénis the species is most allied to the Siphlurus 
aestivalis . 
Siphlurus sp. 
A single, defective specimen S, is present (found 25. VII. 09 at the Kara river). It is 
doubtless a new species. 
