The Collaborative International Dictionary
rhachis
Rachis \Ra"chis\ (r[=a]"k[i^]s), n.; pl. E. Rachises (r[=a]"k[i^]s*[e^]z), L. Rachides (r[a^]k"[i^]*d[=e]z).
(Anat.) The spine; the vertebral column.
(Bot. & Zo["o]l.) Same as Rhachis.
Wiktionary
rhachis
n. (alternative spelling of rachis English)
Wikipedia
Rhachis
Rhachis is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Cerastidae.