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) as did the combatant ships. While at Okinawa "Calamus" was beached as a result of Typhoon Louise, 9 October 1945, refloated 24 October 1945, repaired and returned to service. Following occupation service, "Calamus" returned to San Francisco, California, 20 March 1946 and was struck from the Navy list (date unknown). She was decommissioned 15 May 1946, and transferred to the Maritime Commission 4 September 1946. Final disposition: she was scrapped in 1964. "Calamus" received one battle star for service in World War II. Her crew was eligible for the following medals: USS Calamus (AOG-25) USS "Calamus" (AOG-25) was a "Mettawee"-class