232 ARTHROPODS. 



DIAGRAM XII. 



Crustacean Appendages. 



In this diagram, the appendages of the crayfish are arranged in three 

 groups : — [a) those of the head ; (b) those of the thorax ; (c) those of the 

 abdomen. Most of the figures are taken from Huxley's book on the 

 crayfish. 



Throughout ex. refers to exopodite, en. to the endopodite. 



(a) I, Antennule ; 2, antenna ; 3, mandible, with palp (/.); 4, first 

 maxilla ; 5j second maxilla ; 



{b) 6, first maxillipede ; "], second maxillipede ; 8, third maxillipede ; 

 9, forceps; 10-13, walking-legs; on several the gills {br.'), and the 

 setae of the basal joint or coxopodite {cxd. ) are shown ; on appendage 8, 

 the joints — coxopodite (i'^.), basipodite {i5/. ), ischiopodite (i^.), mero- 

 podite {mp.), carpopodite {cp.), propodite {.pp.), and dactylopodite (dp.), 

 are shown. 



{c) 14, A, copulatory appendage of male ; 14, B, rudimentary first 

 abdominal appendage of female ; 15, second abdominal appendage of 

 male; 16, 17, 18, small unmodified swimmerets; 19, large swimmeret 

 or terminal paddle. 



