=Fam. 4. Anaspidae.=—This includes the remaining pedunculate genera, characterised by the fleshy nature of the mantle and peduncle, which are both entirely devoid of calcifications. The species of _Alepas_ live upon Echinoderms and various other animals; _Chaetolepas_ upon _Sertularia_, and _Gymnolepas_ upon Medusae. _Anelasma squalicola_ is an interesting form, living parasitically upon the Elasmobranch fishes, _Selache maxima_ and _Spinax niger_ in the North Sea. The peduncle is deeply buried in the flesh of the host, so that only a portion of the dark blue capitulum protrudes to the surface. From the whole surface of the peduncle a system of branching processes is given off, which ramify far into the tissues of the fish, and communicate inside the peduncle with the lacunar tissue, which is packed round all the organs of the Cirripede. There can be small doubt that the _Anelasma_ derives its nutriment parasitically through this root-system, since the cirri are mere fleshy lobes unadapted to securing food, and the alimentary canal is always empty. This animal has a suggestive bearing on the Rhizocephala, which, as will be shown, derive their nutriment from a system of roots penetrating the host and growing out from what corresponds morphologically to the peduncle. =Sub-Order 2. Operculata.= [Illustration: FIG. 61.—_Balanus tintinnabulum_, with the right half of the shell and of the operculum removed, seen from the right side. _A_, Antennae, the size of which is exaggerated; _A.M_, adductor muscle; _B_, basis; _C_, carina; _Cr_, cirri or thoracic appendages; _D_, oviduct; _G_, ovary; _L_, lateral compartment; _Lb_, labrum or upper lip; _M_, _M_, depressor muscles of scutum and tergum; _M.C_, mantle-cavity; _O_, orifice of excretory organ; _O.M_, opercular membrane; _R_, rostrum; _S_, scutum; _St_, region of stomach; _T_, tergum. (After Darwin.) ] The “acorn-barnacles” appear later in geological time than the earlier stalked forms. _Verruca_ and _Chthamalus_ are found in the Chalk, and survive down to the present day, but _Balanus_ does not occur until middle Tertiary times. Representatives of the last-named genus are familiar to every one, as the hard sharp objects which cover rocks and piles near high-water mark on every sea-coast. If we examine the hard skeleton of one of these animals, we find that, unlike the Pedunculata, they possess no stalk, the capitulum being fused on to the surface of attachment by a broad basal disc. Typically, there may be considered to be eight skeletal pieces forming the outer ring which invests the soft parts of the animal, an unpaired rostrum and carina, and laterally a pair of rostro-lateral, lateral, and carino-lateral “compartments,” as shown in Figs. 60, 63.