HARD PARTS OF THE CRAYFISH OR LOBSTER. 189 



seven movable joints, working in different planes, so that 

 the limb, as a whole, can move in any direction. 



2. The mouth parts ; the most posterior pair of mouth 

 parts the third maxillipeds cover those anterior to 

 them, and must be removed in order to expose the latter. 



3. The third maxilliped consists of a basal, two-jointed 

 protopodite, and three terminal portions. 



(i.) The epipodite, which is a long, curved plate, which 

 extends into the branchial chamber, and carries a gill, 

 (ii.) A long, slender, many-jointed exopodite. 

 (iii.) A thicker-jointed endopodite. 



4. The second maxilliped is much like the first, but its 

 endopodite is less stout. 



5. The first maxilliped ^ much more slender, and smaller ; 

 its endopodite is flattened and foliaceous ; and the epipo- 

 dite is a simple plate. 



6. The two pairs of maxillae, and the mandibles, are so 

 much like those of the crab, that it is hardly necessary to 

 describe them. 



7. After the mouth parts have been removed, notice the 

 mouth, and, projecting forward over it from its posterior 

 margin, the oval metastoma, covered with short, stiff hairs. 



8. Anterior to the mouth, the large antennas, each of 

 which consists of: 



(i.) A two-jointed protopodite. 

 (ii.) A long, multi-articulate endopodite. 

 (iii.) A flattened, scale-like exopodite. 

 (iv.) On the lower surface of the basal joint of the proto- 

 podite, notice the opening of the antennary gland. 



9. The much smaller antennulw; each of which is made 

 up of a pair of jointed filaments, mounted upon a long 

 protopodite. 



10. On the flat upper surface of the protopodite notice 



