Prominent among the family Ursidae is a polar bear that is adapted to a highly specialized semi-aquatic lifestyle. Although it is a bear yet it is listed as a marine mammal precisely due to the fact that it spends 50% of its life on ice floes and is able to swim as far as 90 km (60 miles).
urchin. 1  a mischievous boy. 2  any small boy or youngster. 3  sea urchin. 4  either of two small rollers covered with card clothing used in conjunction with the cylinder in carding. 5  Chiefly British Dialect. a hedgehog. 6  Obsolete. an elf or mischievous sprite.
Four main species of sea urchins are distributed along the nearshore waters of Southern California: Lytechinus anamesus (white urchin), Centrostephanus coronatus (coronado urchin), Strongylocentrotus purpuratus (purple urchin), and Strongylocentrotus franciscanus (red urchin).here are ten classes in this phylum. Sea urchins are grouped as Echinoidea. Until recently, there was a clear-cut distinction between Echinoidea and other classes because they possess what was believed to be a unique lantern for mastication.