The appendage of the third, consisting of a five-segmented and a . Through fusion of the with the body or with each other, the may seem to consist of fewer . The is usually multi-articulated, it may be supple or very stiff; in the Scyllaridae the is transformed into a single plate-like , similar to the peduncular . The antenna sometimes is named "second antenna", and the , "first antenna". Both, the antenna and the are tactile organs (feelers).