BEV. A. E. EATON ON EECENT EPHEMEEID.E OE MAYFLIES. 385 



15. Fore leg, 16. Intermediate leg, and 17. Hind leg, all x 8 diam. 18. Ventral view of the 

 right tracheal branchia of the foremost abdominal pair, with the lamina placed edgewise, so as 

 to display the fibrils, x 30 diam. 19. Vertical view of the right tracheal branchia of the 2ud 

 abdominal pair, with tlie lamina slightly dejDressed, so as to show the place of its insertion, x 30 

 diam. 20. Right and median caudal sette, x 8 diam. (From France, in fluid.) 



Plate XXVII. 



Joliu Hoeselii. Nymph. 



Figs. 1-24, all enlarged. — 1. Dorsal view of insect shortly before the last moult, in the posture of 

 repose [the legs not quite in perspective]. 2. Ventral view of headless body of the same, 

 showing {t. b.) fibrillose tracheal biauchiic in the region of the neck beside the presternum. 



3. Side view of head and part of the thorax, with fore leg and antenna cut off, x 12 diam. 



4. Underside view of the same, showing [t. b.) branchial fibrils as before, x 12 diam. 



5. Antenna, x 20 diam. 6. Exterior view of labrum, x 20 diam. 7 and 8. Right and left 

 mandibles, x 40 diam. 9. Left 1st maxilla and palpus, -ivith a tuft of [t. b.) branchial fibrils, 

 and pai't of a tendon annexed to the stipes, x 40 diam. 10. Underside, and 11. Upperside 

 views of the labium, 2nd maxilla3, and palpi, x 20 diam. 12. Tongue and paraglossse from 

 above, x 20 diam. 13. Fore leg, and 14. Interior view of the tibial armature, x 12 diam. 



15. Intermediate, and IG. Hind legs, x 12 diam. 17-23. Right tracheal branchite of the seven 

 abdominal pairs numbered successively from the foremost, all x 30 diam. 24. Left tracheal 

 branchia of the third abdominal pair, x 10 diam. (From Toulouse, iu fluid.) 



Plate XXVIII. 



Polymitarcys viryo. Nymph. 



Figs. 1-21, all enlarged. — 1. Dorsal view of $ insect in the attitude of repose, shortly before the last moult. 

 2. Ventral view of the headless body of another specimen. 3. Side view of J head and part of 

 prothorax, x 8 diam. [The " x 30 " belongs to fig. 15.] 4. Underside view and 5. Vertical view 

 of the same, x 8 diam. 6. Antenna, x 20 diam. 7. Labrum x 35 diam. 8. Underside of right 

 mandible, x 20 diam. ; some of the longer hairs were partially erased to make room for fig. 15. 

 9. Upperside of the same, x 20 diam. 10. Part of the left mandible, and 11. corresponding 

 part of the right mandible, placed for the display of the fangs and the molar surfaces, x 30 

 diam. 12. First maxilla and palpus, x 30 diam. 13. Labium, 2nd maxillie, and palpi viewed 

 from above [the lacinia; of the maxillae out of focus], x30 diam. 14. Side view of right 2ud 

 maxilla and palpus, x 30 diam. 15. Dorsal view of tongue and paraglossie, x 30 diam. 



16. Left fore leg, x 12 diam. 17. The same, reversed. 18. Intermediate leg, and 19. Hind 

 leg, X 12 diam. 20. Tracheal branchia of the 1st abdominal pair, x 30 diam. 21. One of the 

 sixth pair, spread out for display of the fringes, x 30 diam. — This Plate underwent considerable 

 alterations at a late period before publication. Most of the figures were drawn from Toulouse 

 specimens; but after these were lithographed, better examples were obtained from Brive. 



Plate XXIX. 



Figs. 1-5. Hexagenia, sp. — Nymph. All enlarged. — 1. Dorsal view of insect about half-growTi. 

 2. Ventral view of head and body of the same. 3. Outside of a tracheal branchia of the 3rd 

 abdominal pair, x 13 diam. 4. The same, reversed ; the divisions of the lamina in both the 

 figures are spread out a little to display the fringes. 5. Right outer and median caudal setas, 

 X 12 diam. (From Mus. Comp. Zool. Cambridge, Mass., in alcohol.) For other details of 

 the nymph of Hexagenia see PI. LXIII. 

 SECOND SERIES. — ZOOLOGY, VOL. III. 45 



