Feather These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular "calamus" (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus). Hatchling birds of some
USS Calamus (AOG-25) USS Calamus (AOG-25) USS "Calamus" (AOG-25) was a "Mettawee"-class gasoline tanker acquired by the U.S. Navy for the dangerous task of transporting gasoline to warships in the fleet, and to remote Navy stations. "Calamus" was launched 4 May 1944 by East Coast Shipyard, Inc., Bayonne, New Jersey, under a Maritime Commission contract; sponsored by Mrs. A. H. Moore; transferred to the Navy 7 July 1944; and commissioned the same day, Lieutenant W. Hord, USCGR, in command. "Calamus" sailed from Norfolk, Virginia, 13 September 1944, bound for Pearl Harbor and Ulithi, where she arrived in mid-December and began her work as