Lateral mass
The lateral masses are the thick, bulky portions forming the entire lateral aspect of the ring of bone. They resemble pillars of support for the skull. Their superior and inferior surfaces have articular facets. Laterally, they project as the transverse processes. These processes, although called transverse processes, are actually a ventral costal process and a dorsal true transverse process. The ventral wall of the transverse foramen is the vestigial homologue of the ribs. The dorsal boundary of the transverse foramen is the true transverse process.