58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



of episternum (fig. 33 B, Eps), the second {71c) on ventral edge of 

 pleural arm (fig. 33 C, PIA), the third {yid) on lateral wall of pro- 

 tergum (fig. 33 A, B) just below ridge h. These groups of fibers con- 

 stitute the most powerful muscle of the leg and function as the de- 

 pressor of the telopodite as a whole. 



72. Reducfor of the femur (fig. 36 A).- — A short, broad muscle 

 in posterior part of trochanter (Tr) arising on ventral wall of the seg- 

 ment ; fibers extending dorsally and posteriorly to posterior rim of 

 base of femur, giving the latter a slight posterior flexion. 



7J. Anterior levator of the tibia (fig. 36 A). — An extremely slen- 

 der muscle arising anteriorly in base of femur; inserted by long, 

 thread-like apodeme on a process from anterior side of base of tibia 

 (as in middle leg, fig. 36 B, lOjAp). 



74. Posterior levator of the tibia (fig. 36 A). — Origin dorsally in 

 proximal part of femur ; insertion by a strong tendon on posterior 

 dorsal angle of base of tibia (as in middle leg, fig. 36 E, 106). 



75. Depressor of the tibia (fig. 36 A). — Origin anteriorly {75a) 

 and posteriorly on ventral wall of femur, with branch {75c) from 

 base of trochanter (Tr) ; inserted by a strong tendinous apodeme aris- 

 ing from small ventral plate in membrane of femoro-tibial joint. 



76. Levator of the tarsus. — Origin on distal third of dorsal wall 

 of tibia; insertion on dorsal lip of base of tarsus. 



77. Depressor of tarsus. — Origin on ventral wall of tibia ; inser- 

 tion on ventral lip of base of tarsus. 



78. Depressor of the pretarsus: retractor of the clazvs (fig. 36 A) . — 

 This muscle comprises three branches, the principal one arising pos- 

 teriorly in base of femur (fig. 36 A, 78), the other two in upper part 

 of tibia ; all inserted on a long tendon extending from femur through 

 tibia and tarsus to unguitractor plate at base of claws. 



The following two muscles are those of the first spiracle, but since 

 the first spiracle is situated within the region of the prothorax, its 

 muscles are to be classed as prothoracic. The mechanism of the spira- 

 cles will be discussed in Section VI. 



7p. Closing muscle of the first spiracle (fig. 51 B). — Origin on 

 ventral process of peritreme (/) ; insertion on lever of posterior lip 

 of spiracle (/)• 



80. Opening muscle of the first spiracle (fig. 51 B). — Origin on 

 ventral process of peritreme; insertion on base of posterior lip of 

 spiracle. 



