Fig. 2.— Astacus fluviatilis.—Dorsal or tergal views (nat. size). A, male; 
B, female :—beg, branchio-cardiac groove, which marks the boun- 
dary between the pericardial and the branchial cavities ; cy, cervical 
groove ; these letters are placed on the carapace ;-7, rostrum ; f, 7’, 
the two divisions of the telson ; 7, eye-stalks; 2, antennules ; 3, 
antenne; 20, lateral lobes of tail-fin ; XV-Xx, somites of the 
abdomen, 
