The thorax in two of the Orders bears no appendages, but in all common Cirripedes it is furnished with six pairs of biramous, multiarticulated cirri, which have a peculiar character, different from the limbs of other Crustaceans, not being natatory, ambulatory, or branchial, but "captorial" or fitted for sweeping the water, and thus catching prey.[11] The cirri, at least the anterior pairs, can, besides other movements, lengthen and shorten themselves; and this Milne Edwards[12] states is the case with the Podophthalmia, and is considered by him as an important character. The cirri of the first pair are attached on each side close to the bases of the mandibles, and, as already remarked, have some claim to be considered as maxillipeds or mouth organs. The three or the four posterior pairs of cirri in the Balanidæ, form a series somewhat distinct from the two or three anterior pairs, thus recalling a characteristic feature in the Edriophthalmia. [11] M. A. Hancock, in 'Annals and Magazine of Natural History,' 2d series, 1849, p. 312, speaks of the cirri acting like a prehensile net. [12] 'Annales des Sciences Nat.,' tom. xviii, p. 121, 1852. The mouth is prominent, and is formed by the partial confluence of the labrum, palpi, and lower segments of the mandibles, and of two pairs of maxillæ; it is capable of movement as a whole; in this respect we are reminded of the Suctorial Entomostracans; but I believe the above type of structure of the mouth is peculiar to Cirripedes.