72 



the third endosternite. It passes outwards, and is inserted 

 on a broad tendon (/. C.) at the inner side of the coxo- 

 podite. 



Basi-ischium. There are two chief muscles. 



The extensor is a small muscle arising from the 

 anterior wall of the third thoracic endosternite. It is 

 inserted on the ventral side of the basi-ischium by means 

 of a small tendon (ex. Ji.). 



The flexor is a larger muscle arising near the origin 

 of the extensor. It is inserted on a long tendon (/. B.) 

 on the dorsal side of the basi-ischium. There is also a 

 small accessory flexor inserted on the outer side of the 

 larger flexor. 



There is one flexor and one extensor for each of the 

 remaining segments of the endopodite. The muscles of 

 the meropodite and carpopodite are fairly large. Those 

 of the propodite and the dactylopodite are small. 



The exopodite has two small muscles— a dorsal 

 extensor and a ventral flexor. 



The flagellum of the exopodite is flexed in its 

 natural position. There is a large extensor muscle (ex. fl.) 

 running the whole length of the exopodite, which is 

 attached to the outer edge of the flagellum and by its 

 action raises the latter. I have not been able to make 

 out a flexor muscle. Probably the flae'ellum falls back 

 into its natural flexed condition by means of the elasticity 

 of the arthrodial membrane. 



The flagellum in each of the maxillipedes is very 

 active, and is constantly moving with great rapidity. 



X. Chela .* (fig. 21, Text fig. 10). 



Coxopodite. There are two muscles — a posterior 



* In all the pereiopods it is probable that those muscles which are 

 situated in the dorsal region of the pleural muscle chambers arise, not 

 only from the walls of the latter, but also from the carapace in this 

 region (PI. IX, fig. 5&,fl.m.) 



