(Chapter 14) Footnote 42:

The atlas differs from other vertebrae in that it (1) articulates at the superior and inferior articular facets of its lateral mass instead of with articular processes, (2) has no corpus, (3) shares no intervertebral disc with the second vertebra, (4) freely rotates above the joint to which it is articulated [articulatio atlanto-axialis mediana], and (5) has no spinous process.