164 THE MORPHOLOGY OF THE COMMON CRAYFISH. 
The third maxillipede is one of the most complete of 
these appendages, and may be advantageously made the 
starting point of the study of the whole series. 
Fie. 44.—Astacus fluviatilis,—The third or external maxillipede of the 
left side (x 3). e, lamina, and 67, branchial filaments of the 
podobranchia ; erp, coxopodite; cas, coxopoditic sete ; bp, basi- 
podite ; ex, exopodite; ip, ischiopodite ; mp, meropodite; cp, 
carpopodite ; pp, propcdite ; dp, dactylopodite. 
Neglecting details for the moment, it may be said that 
the appendage consists of a basal portion (fig. 44, cap, bp), 
