12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



the lateral edge of the aperture connecting body and antennule. It is 

 attached to a tendon on the outer dorsal part of the first joint. The 

 other branch of the remotor arises on the outer anterior border of the 

 aperture, and runs to its attachment on the opposite side of the tendon 

 to which the first branch goes. Both remotors pull the first joint 

 strongly downward toward the body, at the same time rotating it in 

 its socket. 



26. Musculits productovn I antennae (fig. 3). — This muscle arises 

 dorsally on the inner proximal border of the first segment and passes 

 forward to its attachment on the heavy basal membrane on the lateral 

 proximal border of the second segment, on which it exerts a strong 

 downward pull. 



i>7. Musculus reductor 2 I antennae (fig. 3). — This short muscle 

 originates on the inner posterior wall of the first segment and is 

 inserted anteriorly on the membrane of the proximal part of the sec- 

 ond joint. It opposes the productor 2 by bringing the joint upward 

 toward the midline. 



28. Musculus adductor., I antennae (fig. 3). — This is the largest 

 of the four muscles governing the second joint of the antenna. It 

 arises on the inner posterior wall of the first segment and is inserted 

 anteriorly on the membrane at the inner basal part of the second seg- 

 ment. It thus parallels the reductor 2 and nearly conceals it. Like the 

 latter, it brings the second joint upward and toward the midline. No 

 adductor occurs in Astacus in any of the joints of its first antenna. 



2^. Musculus abductor2 I antennae (fig. 3). — This muscle arises 

 on the inner proximal border of the first segment, directly beneath 

 the origin of the productor o, paralleling it almost to its insertion on 

 the membrane below the outer proximal edge of the second segment. 

 It brings the second segment strongly backward and outward. 



JO. Musculus productor 3 I antennae (fig. 3). — This muscle arises 

 on the outer proximal part of the second joint and is attached to the 

 cartilage emanating from the outer proximal edge of the third joint, 

 which is pulled downward and outward by it. 



jj. Musculus reductor 3 I antemiae (fig. 3). — Also arising on the 

 outer proximal wall of the second joint, this muscle goes to its attach- 

 ment on the membrane of the inner proximal border of the third joint, 

 which it brings inward and upward in opposition to the productor 3. 



^2. Musculus reductor 4^ I antennae (fig. 3). — This is the only 

 muscle lying in the third segment. It arises on the inner proximal 

 wall and is inserted on the membrane lying between the two flagella, 

 which are pulled sharply together by its contraction, while the elasticity 



