LESS. XXVII 



EXTERNAL CHARACTERS 



319 



verse depression, the cenncal growe. The carapace is 

 developed from the dorsal and lateral regions of both head 

 and thorax : it is free at the sides of the thorax, where it 



Fig. 81. — Side view of male Freshwater Crayfish, natural size. 



The cephalothorax is covered by the carapace, produced in front into 

 a rostrum (r) and divisible into cephalic {cth) and thoracic (kd) portions 

 separated by an oblique cervical groove. The line from kd jx)ints to 

 the gill-cover. 



The abdomen {ab) is made up of six movably articulated segments 

 (xiv-xix), followed by a telson, the extremity of which is indicated by 

 the lower end of the bracket from ah. 



The eye-stalk is seen at the base of the rostrum. 



Of the cephalic appendages the antennule (a') and antenna (a') are 

 shown ; of the thoracic appendage the third maxilliped (8), the enlarged 

 first leg or cheliped (9), and the four slender walking legs (10-13) 5 of 

 the abdominal appendages three pleopods and the uropod (18). 



(From Lang, after Huxley.) 



forms a flap or gill-cover (Fig. 83, B, Brstg) on each side, 

 separated from the actual body-wall by a narrow space in 

 which the gills are contained. 



From the ventral surface spring a number of paired limbs 



