RachisThe stem of a feather, its lower end being buried in th skin. It is also known as the 'shaft', and its lower end, beyond the level of the lowest barb, is called the 'calamus' or 'quill'. To either side of the rachis the web is attached. The term may also be spelt 'rhachis'.
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From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver