Both Uses

extraneous
in
Atlas Shrugged
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His mouth was the one part of him which he could not pull tight at any time; it was uncomfortably prominent in his lean face, attracting the eyes of any listener: when he spoke, the movement ran through his lower lip, twisting its moist flesh into extraneous contortions of its own.†
Chpt 1.10 *

extraneous = not relevant or important to the matter under consideration
This was only a small, extraneous stab of pain, he thought, a feeling of disappointment in an expectation he had never had the right to expect; he should have known that this was just what a man like Francisco d'Anconia would do-and he wondered angrily why he felt as if a bright, brief flame had died somewhere in a lightless world.†
Chpt 2.1

Definitions:

(1) (extraneous)
not relevant or important to the matter under consideration
(2) (meaning too rare to warrant focus)
More rarely, extraneous can refer to something that does not belong to that in which it is contained (as in "water free of extraneous matter"); or to something coming from an outside source (as in "Extraneous light in the camera spoiled the photograph.")