146 ELEMENTARY BIOLOGY. [XII. 



b. The great chelce : closely resembling the last 

 appendage in structure, but much larger and 

 more powerful ; it carries a gill. 



c. The three maxittipedes. 



a. The most posterior : its short thick basal 

 joint (protopodite) : the three prolongations 

 articulated to it; the external (epipodite) a 

 curved elongated lamina lying in the branchial 

 chamber and bearing a gill ; the middle one 

 (exopodite) long, slender and many-jointed ; 

 the internal one (endopodite) several-jointed 

 and much resembling one of the ambulatory 

 limbs. 



ft. The middle maxillipede : much like a. but 

 with a less stout endopodite. 



7. The anterior maxillipede ; protopodite, exopo- 

 dite and epipodite much like those of /3. but 

 smaller and the epipodite bearing no gill ; the 

 endopodite flattened and foliaceous. 



The ambulatory limbs, great chelae, and max- 

 illipedes together constitute the appendages of 

 the thorax; we now come to those of the head 

 proper. 



d. The two maxillce. 



a. The- posterior: its basipodite and endopodite 

 essentially like those of the anterior maxilli- 

 pede ; the epipodite and exopodite united and 

 forming a wide oval plate (scaphognathite) 

 which lies at the anterior end of the gill- 

 chamber (11. 7.). 



