1330 CRUSTACEA. 



fig. h) .. There is a small flexor of this joint, attached to the posterior 

 apex of the basal joint. 



The maxillaz are provided with but few small muscles, requiring no 

 remarks. 



The feet of the first pair are remarkable for having as various 

 motions as could be afforded bj a ball and socket joint. This arises 

 from their insertion on a fleshy prominence. To produce these 

 various motions, each leg is provided with five muscles radiating from 

 the base, some of which are of very peculiar form. Four of these 

 muscles are inserted into the base of the first joint, and one along its 

 posterior margin. The latter appears to be attached to the back near 

 the median line, a short distance behind the eyes (g, fig. h). Of the 

 remaining muscles, two pass forward and outward (h, i, fig. a and fig. 

 h), one directly outward, and the fourth (k, fig. h) backward and out- 

 ward. The most anterior (h) is a slender muscle, attached just exte- 

 rior to the base of the first pair of maxillipeds. The second (i, fig. a 

 and fig. h) is composed of two- parts inserted into the same tendon. 

 These parts continue together through half their length, then separate, 

 and soon after each divides into two nearly equal portions, which 

 diverge under the large curved spine, and pass to their attachment at 

 the margin of the shell. 



The base of the second pair of feet has a narrow prolongation, 

 which affords attachment to two muscles ; one passes posteriorly, and 

 is attached near the articulation of the head and thorax (m, fig. A), 

 another extends outward in front, beneath the extremity of the adja- 

 cent spine. Two other short muscles are inserted at the base of the 

 prolongation, and are also attached near the spine ; one on the back, 

 and the other below. The last of the muscles moving this pair of 

 legs extends outward, and is attached to the epimeral articulation (1, 

 ng. h),. 



The terminal claw is provided with flexor museles of great strength. 

 A large conical muscle attached along the whole posterior margin, is 

 inserted in a bony tendon extending from the inner portion of the 

 base of the claw. Another large muscle arises from the basal portion 

 of the joint, and is inserted into the preceding muscle a short distance 

 from its insertion. There is the same arrangement in the female (fig. 

 c). A small extensor is inserted in the outer part of the base of the 

 claw, and attached to the outer posterior margin of the first joint. 



