. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 296 ECHIKODERMATA. lacral branchise upon a rosette formed of large pores on the dorsal surface (fig. 239). The locomotive feet are very small in Clypeastridce, and are distributed either over the whole surface of the ambulacra, or' are confined to branching rows upon the ventral surface. In the Spatamjidfe there are peculiar bands upon the upper surface, the fascicles or semitce (fig. 239), upon which, in place of the spicules, knobbed bristles with active cilia (clavulce) are distributed.
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 296 ECHIKODERMATA. lacral branchise upon a rosette formed of large pores on the dorsal surface (fig. 239). The locomotive feet are very small in Clypeastridce, and are distributed either over the whole surface of the ambulacra, or' are confined to branching rows upon the ventral surface. In the Spatamjidfe there are peculiar bands upon the upper surface, the fascicles or semitce (fig. 239), upon which, in place of the spicules, knobbed bristles with active cilia (clavulce) are distributed. Develop- ment takes place with a Pluteus larval stage, in which the larva is provided with ciliated epaulettes or with an apical rod. The Sea-urchins live, as a rule, near the coast, and feed on molluscs, small marine animals, and Fuci. Some species of Echinus have the power of boring holes in the rocks in which they live. We find many fossil shells, especially in the FIG. 239.—Brissopsi* lynfera with the fascicles or Semites surround- ing the rosette. A, anus. Order 1.—CIDABIDEA=REGULAR SEA-URCHINS. Echinoidea with central mouth and equal band-like ambulacra ; ivith teeth and masticator)/ apparatus ; with sub-central anus in the apical space. Fam. Cidaridae. With very narrow ambulacra! and broad iaterambulacral areas, on both of which are large perforated tubercles and club-shaped spines. There are no oral branchise. Cidaris metiilaria Lam., Plu/ll acanthus imperialis Lam., East Indies. Fam. Echinidae. Sea-urchins. The pores are grouped in transverse rows ; there is a round, thin shell, broad ambulacral spaces bearing tubercles and spines, which are mostly short and pear-shaped. Oral branchirc are present. ni'//xf<'x i-itrh'i/utiix. Lam., Echinus mdo Lam., Strongylocentrotus Hri/fun Brit. saxatllis Lin., Mediterranean. Fam. Echinometridse. With long oval shell, imperforate tubercles and oral branchia?. Ki-liiinniirira oblong a Blainv., PodopJiora atruta
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