The riddle of trilobites limbs was finally solved just in second
half of the 19th century (Walcott, Beecher).
The limbs of the arthropods have different functions like movement, sensory
perception or feeding. Regarding to this the trilobites are comparable with
their recent relations of tribe, the Crustacea.
The strongly segmented (movability) antennas projecting
from the hypostomes lateral notches beyond the doublure.
The limbs (ventral appendage) are paired. The anterior limbs being of use of
perception of food and feeding, care of brood asm.. On the other hand the
primary use of the thoracic limbs is locomotion, however sometimes at predaceous
representatives of trilobites the use of this limbs was the fixing of prey. In
opposite to their recent representatives all ventral appendages are developed
nearly isogenous. That is there's no functionally significant scructure or in
other words, there's no variation of cleft feet to specialized structures (e.g.
mouthparts for use of dissection of food, or only specialized for locomotion).