318 EEV. A. E. EATON ON EECENT EPHEMERID.E OE MAYFLIES. 



5. Seven uniform pairs of abdominal tracheal branchite, the foremost ventral : laminse small, 

 coriaceous, snbrotund. Median lobe of tongue acute. Maxilke ii coherent, enclosing and 

 intimately adherent to the labium. At maturity the space between the wings and the peak of 

 the mesonotum is spanned over by membrane sheathing the base of the dorsum. 



Oligoneuria, p. 29, PI. XXVI. 

 .. Seven uniform latero-dorsal pairs of abdominal tracheal branchite ; the laminaj well developed, 

 foliaceous, and somewhat obovate. Labium and terminal margins of the fore wings free. 

 Median lobe of tongue obtuse. Caudal setae natatorial Jolia, p. 43, PI. XXYII. 



6. Frons armed anteriorly with a single obtuse median protuberance. Tusks of mandibles con- 

 nivent when closed together i/e*Y/5^e?iJa, p. 48, Pis. XXIX. & LXIII. (part). 



.. Frons armed anteriorly with two acutely conical projections. Tusks of mandibles overlapping 

 at the points when closed together Ephemera, p. 58, PL XXX. 



7. Palpus of maxilla i quadriarticulate *. Maxillse ii concrete with the labium, which is undivided. 

 General form testudinate, broadly ovate, flattened beneath and highly convex dorsally. Caudal 

 setffl plumose, very short, retractile with the last segment. Tracheal brauchite concealed by a 

 large notal shield in which the anterior wings are immersed at maturity. 



Prosopistoma, p. 149, PI. XLIII. 



.. Palpus of maxilla i triarticulate 8 



,, „ apparently f biarticulate [but if triarticulate, — Mandibles short. Lacinia 



of maxilla i curved externally from the point to the insertion of the palpus, which is longer tlian 

 it. Seven pairs of abdominal tracheal branchiae. Lobes of the labium narrow &c., — cf. §18 

 below]. Tracheal branchiae all foliaceous and double, with unequal divisions. 



Calllba'tis, p. 191, PL XLVIII. 



8. Mandibles short 9 



„ 2'1'olongcd beyond the head into slender incurved tusks. Six uniform pairs of abdo- 



minal tracheal branchiae : the laminae jugate, narrowly lanceolate, conduplicatc lengthwise and 

 fringed. Median lobe of tongue excised. Frons unarmed anteriorly. 



Euthyplocia, p. 37, PL XXIX. (part) . 



9. Lacinia of maxilla i truncate for some distance outwards from the point ; consequently, between 

 the point and the insertion of the palpus, the exterior contour of the lacinia is angular : a 

 conspicuous dense patch of suberect hair occupies some part or the whole of the truncated edge : 

 palpus longer than the lacinia 10 



.. Lacinia of maxilla i curved or irregularly rounded off from the point to the insertion of the 

 palpus 14 



10. Six pairs of abdominal tracheal branchiae, all of uniform make ; each branchia consisting of 

 two jugate, elongate-oval, plumose or piunately parted laminae, with crowded subulate segments 



Potamanthus, p. 78, PL XXXI. 

 .. Seven pairs of abdominal tracheal branchije 11 



11. Tracheal branchiae uniform 12 



.. Foremost tracheal branchiae quite different in form from the other pairs 13 



12. Tracheal branchiie bipartite, with subulate or linear-lanceolate divisions. 



Leptophh'hia, p. 92, PL XXX IL 



* The biisis or place of insertion of the palpus might iu many iustauces be easily mistaken for a joint i^c.rj. in 

 SqMurus, PL L). 



t The number of joints could not be positively ascertained from the specimens examined. Even the figure 

 published is suggestive of there being possibly a very short third joint at the tip of the palpus ; but no joining was 

 traceable thereabouts in the actual oljuct. — A. E. E. 



