Pacific Ocean, Western region

The seaward boundary of the western region is marked by a broken line of oceanic trenches, extending from the Aleutian Trench in the north through the Kuril and Japan trenches and southward to the Tonga and Kermadec trenches, terminating close to the northeast of North Island, New Zealand. Its structure is more complex than that of the eastern region. Characteristically

Najd

Also spelled �Nejd, � region, central Saudi Arabia, comprising a mainly rocky plateau sloping eastward from the mountains of the Hejaz. On the northern, eastern, and southern sides, it is bounded by the sand deserts of an-Nafud, ad-Dahna', and the Rub' al-Khali. It is sparsely settled, except for the fertile oases strung along the escarpment of Jabal (mountains) Tuwayq and the al-'Aramah plateau. The arid

Malacostracan, The nervous system and sensory organs

The malacostracan central nervous system consists, in primitive forms, of a ventral nerve cord and ganglia within each body segment. The supraesophageal ganglion innervates the eyes, antennules, and antennae, and the subesophageal ganglion innervates the mouthparts of the head region. In amphipods and anomuran decapods the ganglia of abdominal segments are