1915.] NATURAL SCIENCES OF PHILADELPHIA. 513 



Hypopygial Structures. 

 Lateral aspect of the hypopygium of T. mainensis. 



" T. penobscoi. 

 " T. taughannock. 

 " T. kennicotti. 

 " T. monlicola. 

 " T. tuscarora. 

 " T. Seminole. 

 " T. rangiferina. 

 " T. mandan. 

 " T. johnsoniana. 

 " T. morrisoni. 

 " T. megaura. 

 " T. parshleyi. 



Plate XIX. — Hypopygial Structures. 



8s = eighth sternite ; 9s = ninth sternite ; 91 = ninth tergite. 

 Fig. 44.— Dorsal aspect of the ninth tergite of T. algonquin. 



Plate XX. — Hypopygial Structures. 



Fig. 61. — ^Pleural appendages of T. algonquin; lateral aspect. 



Fig. 62. — Ninth pleuro-sternite of T. taug/ian/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 pleiu*al 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. loewiaJia; lateral aspect. 

 Fig. 68. — Pleural appendages of T. mingwe; lateral aspect. 

 Fig. 69. — Inner pleural appendage of T. monlicola; lateral aspect. 

 Fig. 70. — Inner pleural appendage of T. rangiferina; lateral aspect. 

 Fig. 71. — Second pleural appendage of T. mandan; lateral aspect. 

 Fig. 72. — Inner pleural appendage of T. mandan; lateral aspect. 

 Fig. 73. — Outer pleural 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. 



