22 EEV. A. E. EATON ON EECENT EPHEMEEID^ OE MAYFLIES. 



Group III. 

 Series I. 



Section 10 of Siphlurus Genera 32-36. 



„ 11 oi Btetisca » 37. 



Series II. (provisional). 



Section 12 (provisional) Gemis Plate LII. 



Series III. 



Section 13 of Atopopus Genera 38-10. 



,, \-i oi Ecihjurus „ 41-46. 



It may be noted of tlie foregoing Table that the composition of the section of Folymt- 

 tarcys is not altogether homogeneous. Genus 7, Ei(thi/plocia, may eventually have to 

 rank as a separate section, on account of its triarticulate palpi. 



Section 8 is associated in the same series as section 7, because the adult Prosopistoma ? , 

 in the construction of its head and thorax, is, according to M. Vayssiere's representation, 

 very similar to Ccenis. This last genus, ' in some particulars, resembles insects of the 

 Folymitarciis section ; but, on account of the formation of the nymph, it appears to be 

 more nearly related to the section of Ephemerella than to the genera of section 2. 



The provisional section 12 is classed in Group III. on account of the nymph having 

 some resemblance to genera of section 10 in the form of the laciniae of its lower maxillae 

 and the lobes of the labium. On the other hand, its hinder tracheal-branchiaj are con- 

 structed after the same plan as those of the genera in section 14. As a matter of pure 

 conjecture, it may be suspected of belonging to section 13, of which no nymphs have 

 hitherto been seen ; only if such were the case, it is probable that the tibiae would be 

 somewhat shorter than they are in comparison with the tarsi. 



Systematic Description, 

 group i. of the genera. 

 Adult. — At the fore-wing roots the anal nervure (8) meets the pobrachial nervure (7) ; 

 the hinder tarsi, when not atrophied, have four distinct joints, and sometimes an ill- 

 defined fifth joint intimately concrete Avith the tibia ; 6 oculi evenly contoured. 

 Nijmxjli. — Palpi of the 2nd maxillae (" labial palpi ") 2-jointed (except Euthyplooiu, 



3-jointed). 



First Series of Group I. 



Legs of the adult ? short in proportion to the body, and feeble, when not functional- 

 less, through atrophy of the tibia and tarsus ; the fore legs in both sexes of the subimago 

 extremely short, and transversely rugose ; hind legs of adult 5 the longest pair. Nymph. 

 Palpi of 1st maxillEe very stout, 2-jointed (excej)t Euthyplocia 3-jointed) and curved. 



Section 1 of the Genera. — Type of Faliugenia. — Subcosta of the fore wing, when de- 

 veloped, retired within a fold of the membrane somewhat beneath the radius. In many 

 genera the subimaginal pellicle of the wings is not shed at the last moult. Nymjjh fos- 

 sorial or predatory ; in those that are known the median lobe of the tongue is pointed. 



Subsection A. Wing-neuration complete and plentiful ; anal nervure (8) of the fore 

 wing either sinuous, or else from the wing-roots to its fork nearly straight, and afterwards 

 gently arched; axillary nervures short but strong; the first (9') annexed to the anal 



