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.
The green sea urchin is an echinoderm, which means it belongs to a group of radially symmetrical, invertebrate animals that includes starfish, sand dollars and sea cucumbers. There are several urchin species distributed in boreal waters around the world, but only the green sea urchin, which has one of the longest scientific names (Strongylocentrotus droebachiensis), is found in the Gulf of Maine.