Note 45 — Chapter V · CRUSTACEANS.—PRAWN, SHRIMP, MYSIS, CRABS; AMPHIPODS; ISOPODS

‘A limb is chelate when it has joints that will act together like a pair of tongs. Generally this character is produced by the hinging of the seventh joint a considerable way down on the side of the sixth. When the seventh joint, or finger, can be folded back upon the sixth, although the latter is not produced into any thumb-like process to oppose it, the limb is then said to be sub-chelate, the claw being in that case partial, though often extremely efficient.’ Stebbing, Crustacea (International Science Series, lxxiv), p. 45.