40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



originates mesally on the prolongation of the endopleurites where they 

 come together just below the attractor of the epimera. It travels ven- 

 trally for half its length, separated from the visceral cavity only by a 

 very thin sheet of tissue. It passes at last into the fifth thoracic seg- 

 ment behind branch a of the promotor, where it finally attaches itself 

 to the same tendon. The third branch (c) originates on the lateral 

 part of the membrane covering the anterior promotor of the fifth 

 pereiopod, which extends forward through the thorax as previously 

 stated. The most lateral branch (d) originates on the lateral anterior 

 surface of the intermediate endopleurite, being inserted beside branch 

 c on the broad tendon common to all branches of the promotor. The 

 contraction of this muscle causes the leg base to be moved strongly 

 forward. 



72J. Musciilus remoter (fig. 12 F). — As in the first leg, this is 

 the only vmbranched muscle belonging to the leg base. It arises on the 

 anterior surface of the endopleurite separating the fifth and sixth 

 thoracic segments, passing downward and outward to its tendinous 

 insertion on the upper postaxial border of the coxopodite. It opposes 

 the promotor. 



124 a-d. Musculus levator a-d (fig. 12 D, E). — This heavy muscle 

 appears to be divided into four main parts, although the third and 

 fourth are not very distinct from each other. The first branch (0) 

 arises on the posterior surface of the endosternite between the fourth 

 and fifth thoracic segments and is inserted by an extremely strong 

 tendon on the upper (in this case postaxial) border of the basi-ischio- 

 podite. A second branch (&) arises on the lateral part of the mem- 

 brane encasing the anterior promotor of the fifth pereiopod. The two 

 remaining branches (c and d) arise close together, on the anterior sur- 

 face of the endosternite between the fifth and sixth thoracic segments, 

 and are inserted between branches a and b on the same strong tendon. 

 The entire muscle causes the leg to be raised. 



12 f, a-e. Muscidus depressor a-e (fig. 12 D, E, F). — The first 

 branch (a) originates mesally on the posterior surface of the en- 

 dosternite separating the fourth and fifth thoracic segments, as well 

 as on the sternal wall of the fifth segment. It is inserted on the lower 

 (in this case preaxial) rim of the basi-ischiopodite. A very short 

 branch (&) runs from the anterior part of the coxopodite to the same 

 insertion, while a similar short branch (c) originates in the rear of 

 the coxopodite. A slightly longer branch (d) begins on the outer part 

 of the sternal wall near the endosternite between the fifth and sixth 

 thoracic segments. The longest branch (e) originates on the anterior 

 wall of the endopleurite separating the fifth and sixth segments, com- 



