Full Idea
Many identify the cognitive with the conscious, and it seems far from plausible that consciousness extends outside the head in these cases. But not every cognitive process, at least on standard usage, is a conscious process.
Gist of Idea
Consciousness may not extend beyond the head, but cognition need not be conscious
Source
A Clark / D Chalmers (The Extended Mind [1998], §3)
Book Reference
-: 'Analysis' [-], p.3
A Reaction
This gives you two sorts of externalism about mind to consider. No, three, if you say there is extended conceptual content, then extended cognition processes, then extended consciousness. Depends what you mean by 'consciousness'.