124 EEV. A. E. EATOX OX EECENT EPHEMEEID.E OR MAYFLIES. 



AntennjE inserted upon the disk of tlie frons. Terminal joint of the 

 palpus of maxilla i. about f as long as the remainder; joint 2 less than 



i as long as joint I PI. XL. 1-17. 



Nos. 1 and 4-7 of the abdominal segments bear tracheal branchire; the 

 first is subulate and erect ; the others are of normal structure, their 

 lamiuse ovate-oblong and compactly stratified ; the laminse of those of 

 segment 4 are each traversed by a slight furrow from side to side beyond 

 their middle, serving as a hinge. Caudal setffi plumose. Antennie in- 

 serted upon the disk of the frons. Palpus of maxilla i. lost [or aborted ?] Pis. XL. 18-20 & LXIV. 3-8. 



EPHEMERELLA, Walsli, 1862. 



Illustrations. Adult (details), PL XIV. 21 a-c [wings, legs, d head and genitalia] ; 

 Etn., Trans. Eut. Soc. London (1871), pi. ii. 5 [part of fore wing] : — (whole figures) see 

 under E. ignita, synonyms Potanianthus, Pictet, op. cit. pis. P>0, 31, & 33, Ni/mph, 

 PL XXXVII. ; also Pictet, op. cit. pis. 29 & 33, and Vayssiere, Ann. des Sc. Nat. (6) xiii. 

 pLviii. 74 &c. (1882). 



Adult. — Hind wing of moderate size, unevenly arcuate in front, with a very shallow 

 marginal depression just heyond the most salient portion of the costa; the subcosta (2) 

 advancing from the wing-roots in a bold curve towards that prominence, proceeds, in 

 proximity to the costa from thereabouts, almost in a direct course towards the obtuse 

 extremity of the wing, and meets the margin obliquely rather near the termination of 

 the radius (3) ; this last nervure, more gently curved, approaches the subcosta gradually, 

 and attains the tip of the wing : the intercalar neuration is well developed, and cross 

 veinlets are numerous. In both wings most of the intercalary veinlets remain isolated 

 and rudimental, comparatively few of them obtaining connection with longitudinal 

 nervures. Cross veinlets plentiful in the larger portion of the fore wing, but scarce or 

 absent in the immediate vicinage of the terminal margin and within tlie area bounded 

 anteriorly by the anal (8) nervure, and absent from the marginal area before the 

 buUa ; those of the pterostigmatic space, in all the described species, are for the 

 most part divided near the costa, and their branchlets intercommunicate so as to 

 enclose a series of small irregular cellules upon the costa. In the anal-axillar 

 interspace of the same wing are 3 long intercalar nervures, and as few or fewer short 

 isolated rudiments of others, one of the latter usually standing in the interval 

 between the first and the second of the former. Of the three longer intercalars quoted, 

 the intermediate is the longest ; and this is connected Avith the anal jiervure either 

 directly (turning aside a little, anteriorly, to unite with it as a branch) or indirectly (by 

 blending with a cross veinlet), and sometimes, in addition to that terminal connection, a 

 cross veinlet establishes further communication between them. In like manner the first 

 of the three may be connected directly or indirectly with the anal nervure, and the third 

 with the second intercalar ; otherwise the first rcmnins isolated, and the third is simul- 

 taneously in communication both with the first axillar (9') and with the intermediate 

 intercalar nervures by uniting at its inward extremity with cross veinlets [compare Etn., 

 op. supra cit. pi. ii. 5. Pictet's figui'e, Pict. op. ibidem cit. pi. xxxii. 1, is untrustworthy 

 in detail]. Guard at the aperture of the mesothoracic spiracle small and triangular; 

 Eorceps-limbs of 6 3-jointedj stout, the intermediate joint long, the others ver^ short. 



