1915.] NATURAL SCIENCES OF PHILADELPHIA. 513 
Plate XVIll. — Hypopygial Structukes. 
Fig. 31. — Lateral aspect of the hypoj)ygium of T. tnaincnuis. 
Fig. 32. — " " " " " " T. pcnobacol. 
Fig. 33. — " " " " " " T. laughannock. 
Fig. 34.— " " " " " i' T. kennicotli. 
Fig. 35.— • " " " " " " T. morUicola. 
Fig. 36. — ■ " ," " " " " T. tuscarora. 
Fig. 37.— " " " " " " T. seminole. 
Fig. 38. — ■ " " " " " " T. rangiferina. 
Fig. 39.— " " " " " " T. mandan. 
Fig. 40. — ■ " " " " " " T. jolinsoniana. 
Fig. 41. — ■ " " " " " " T. morrisoni. 
Fig. 42.— " " " " " " T. megaura. 
Fig. 43.— " " " " " " T. parMeyi. 
Plate XIX. ^-Hypopygial Structures. 
8s — eighth sternite ; 9s = ninth sternite ; 91 = ninth tergite. 
Fig. 44. — Dorsal aspect of the ninth tergite of T. algonquin. 
T. peiiobscol. 
T. mainensis. 
T. laughannock. 
T. kennicotti. 
T . cayuga. 
T. triton. 
T. loewiana. 
T. vianlicola. 
T. tuscarora. 
T. seminole. 
T. rangiferina. 
T. mandan. 
T. dietziana. 
T. johnsoniana. 
" T. megaura. 
" " T. parshleyi. 
Plate XX. — Hypopygial Structures. 
Fig. 61. — Pleural appendages of T. algonquin; lateral aspect. 
Fig. 62. — Ninth pleuro-sternite of T. tau^/irtM/iocA-; ventral aspect; a = fleshy 
lobe. 
Fig. 63. — Pleural appendages of T. cayuga ; lateral aspect; d = dorsal arm; 
V = ventral arm. 
Fig. 64. — Pleurite of T. tuscarora; ventral aspect. 
Fig. 65. — Outer pleural appendage of T. triton; lateral aspect. 
Fig. 66. — Apex of inner pleural appendage of T. triton; lateral aspect from 
the inside. 
Fig. 67. — Pleurite of T. loewiana; lateral aspect. 
Fig. 68. — Pleural appendages of T. mingive; lateral aspect. 
Fig. 69. — Inner pleural appendage of T. monticola; lateral aspect. 
Fig. 70. — Inner pleural appendage of T. rangiferina; lateral aspect. 
Fig. 71. — Second pleural appendage of T. mandan; lateral a.spect. 
Fig. 72. — Inner pleural appendage of T. mandan; lateral aspect. 
Fig. 73. — Outer pleui-al appendage of T. dietziana; lateral aspect. 
Fig. 74. — Appendages on the tip of the ninth sternite of T. parshleyi; lateral 
aspect. 
Plate XXI. — Hypopygial Structures. 
Fig. 75. — Penis-guard of T. mainensis; ventral aspect. 
Fig. 76. — Apex of the inner pleural appendage of T. mainensis; lateral 
aspect. 
Fig. 77. — Penis-guard and gonapophyses of T. seminole; lateral aspect. 
Fig. 78. — Gonapophyses of T. triton; lateral aspect. 
Fig. 79. — Penis-guard of T. triton; lateral aspect. 
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