The last-named species has a straight symmetrical abdomen, with the penultimate segment expanded and strongly calcified to form a back-door to the very unconventional habitation.
In others, which represent the perichordal type, the greater share of the formation of the whole vertebra falls to the (paired) dorsal cartilage, but there is in addition a narrow ventral or hypochordal cartilage which fuses with the dorsal or becomes connected with it by calcified tissue; the notochord is thus completely surrounded by a thick sheath in tadpoles with imperfectly developed limbs.
Stomach generally provided with chitinous or calcified masticatory plates.
The body-wall is extensively calcified in the Cyclostomata and in most Cheilostomata, which may form elegant network-like colonies, as in the unilaminar genus Retepora, or may consist of wavy anastomosing plates, as in the bilaminar Lepralia foliacea of the British coasts, specimens of which may have a diameter of many inches.
Not looking at the calcified stumps of a close-growing grove of palms.
In one or two cases the epithelium of the foot secretes a calcified shell, which is either free as in Argonauta or adherent as in Hipponyx.
They secrete a cuticle which never approaches in thickness the often calcified cuticle of Arthropods.
In the Cyclostomata, further distinguished by the cylindrical or prismatic form of their highly calcified zooecia, the orifice is typically circular, without any definite closing organ.
Though the exterior is more uniform than in most groups of Crustacea, the bivalved shell or carapace may be strongly calcified and diversely sculptured (fig.
The Axifera comprise those corals that have a horny or calcified axis, which in position corre sponds to the axis of the Pseudaxonia, but, unlike it, is never formed of fused spicules; the most familiar example is the pink sea-fan, Gorgonia cavolinii, which is found in abundance in 10-25 fathoms of water off the English coasts (fig.