EEV. A. E. EATOX ON EECEXT EPHEMEEID.E OE MAYFLIES. 317 



50 .... Second joint of tlie hind tarsus equal to the third 



joint 51 



„ .... Second joint of the hind tarsus longer than the 



third joint 52 



51 .... Penis-lobes somewhat explanate and oblong, sub- 

 truncate at their divergent extremities. Femora usually 



without markings, but sometimes faintly banded . . . Heptagenia [part] (p. 265). 



,. .... Penis-lobes broad and short. Femora banded . Heptagenia [^iW^^^.^Ql). 



Penis-lobes narrow and subcylindrical at their 



bases, with suddenly enlarged patulous tij)s. Femora 



without markings Fagnoides (p. 261). 



52 . • - • Femora usually without markings, &c. [See 51 



above.] iZ<'^;^*^e»/« [part] (2x265). 



Femora usually marked with a dark median spot 



or streak, &c. [See -19 above.] it///7/«'o<7e?2a[part](p.250). 



Analytical Index to the Descriptions and Illustrations of Nymphs of 

 Ephemerkl(B contained in this Volume. 



1. Palpi of maxilla II biarticulate 2 



„ „ triarticulate 7 



„ ,, phiriarticnlate, flagellate, cacli consisting of a long, stout basal joint and a 

 slender, multiarticulatc flagellnm. Seven pairs of abdominal tracheal brancliire : the foremost 

 different in shape from the others. A. iv-imeless S. American nymph p. 22'J, PI. LIII. 



2. Basal joint of the palpus of maxilla ii shorter than the other joint. Palpus of maxilla i 



also biarticulate 3 



.. Basal joint of the palpus of maxilla ii subequal in length to the other joint. Palpus of maxilla 



I triarticulate. Median lobe of tongue excised. Seven pairs of abdominal tracheal branehite ; 



the foremost branchiae rudimentary, minute and fringeless ; the other branchiae ciliate or 



fimbriate. Habits fossorial 6 



.. Basal joint of the palpus of maxilla ii longer than the other joint, which is peculiarly pouched. 



Palpus of maxilla i likewise biarticulate. Seven pairs of abdominal tracheal branchi;e. Lobes 



of the labium more or less distant from one another. Type of Ecdi/urus. 



See Tabulation at p. 23,-3, Pis. LIV.-LXII. 



3. LaminfE of at least the hinder pairs of the abdominal tracheal branchite jugate, narrow, con- 

 duplicate lengthwise and fringed. Habits fossorial 4 



.. Laminte of the abdominal tracheal branchife all single, broad, somewhat plane, fringeless, and 

 each provided at its base with a fascicle of fibrils. Habits prcdaceous 5 



4. Six pairs of abdominal tracheal branchi:e all of uniform make. Median lobe of tongue acute. 

 Mandibles strong and short Palingenia, pp. 23 & 25, PI. XXV. 



.. Seven pairs of abdominal tracheal branchire ; the foremost, unlike the others, is rudimentary, 

 minvite, single and spathulate. Median lobe of tongue obtuse. Crown of mandible prolonged 

 into a slender tusk in advance of the head Po///;/»7«rcys, p. 44, PL XXVIII. 



Ji 



