THORACIC AND HEAD APPENDAGES. 149 



a gill and coxopoditic setae; and basipodite, 

 bearing endopodite and exopodite. 



ii. The endopodite consists of five segments. The 

 first segment is the largest and is fused with 

 the basipodite. 



iii. The exopodite is slender, and consists of a long 

 proximal segment and a distal many -jointed 

 filament. 



VII. The second maxillipede is smaller and less firmly 

 calcified than VIII., which it resembles in form ; 

 but the exopodite is larger than in VIII., and 

 the endopodite smaller, and all its joints are 

 movable. 



VI. The first maxillipede is smaller and softer than 

 VII. 



i. The two segments of the protopodite are ex- 

 panded on the inner side, forming a large two- 

 lobed lamella. A broad plate, the epipodite, 

 takes the place of a gill. 



ii. The endopodite is very small and two-jointed. 



iii. The exopodite resembles that of VII. 



In the Continental variety (Astacus fluvi- 

 atilis) a small gill is present attached to this 

 limb. 



3. The head appendages consist of three pairs of oral 

 appendages or jaws, V. to III., placed at the sides of 

 the mouth, and two pairs of pre-oral appendages, 

 II. and I., at the front. of the head. 



Fig. 35. Astacus pallipes, var. nobilis. The oral appendages of the 



right side seen from below : x 2. (c. h. h.) 

 HI, the mandible. IV and V, the first and second maxillae. VI, VH, 



and Vni, the three maxillipedes. 



A, region of attachment to body-wall. AB and AD, points of insertion 

 of abductor and adductor muscles of mandible. B, basipodite. C, D, I, M, P, 

 joints of endopodite. CX, coxopodite. E, epipodite. F, pivots of mandible. 

 G, gill. H, coxopoditic setee. N, endopodite. S, scaphognathite. X, first 

 segment of exopodite. 



