rhachi

a. Of or pertaining to the rhachis; as, the rhachidian teeth of a mollusk. [ 1913 Webster ]

‖n. pl. [ NL. See Rhachis, and Glossa. ] (Zool.) A division of marine gastropods having a retractile proboscis and three longitudinal rows of teeth on the radula. It includes many of the large ornamental shells, as the miters, murices, olives, purpuras, volutes, and whelks. See Illust. in the Appendix. [ 1913 Webster ]

‖n. [ NL., fr. Gr. "ra`chis the spine.] (Bot.) A branch of inflorescence; the zigzag axis on which the florets are arranged in the spikelets of grasses. [1913 Webster]

a. [ Gr. "ra`chis, -ios, the spine + &unr_;&unr_;&unr_;, &unr_;&unr_;&unr_;, a tooth.] (Zool.) Having gular teeth formed by a peculiar modification of the inferior spines of some of the vertebrae, as certain South African snakes (Dasypeltis) which swallow birds' eggs and use these gular teeth to crush them. [1913 Webster]

‖n.; pl. E. Rhachises L. Rhachides [ See Rachis. ] [ Written also rechis. ] 1. (Anat.) The spine. [ 1913 Webster ]

2. (Bot.) (a) The continued stem or midrib of a pinnately compound leaf, as in a rose leaf or a fern. (b) The principal axis in a raceme, spike, panicle, or corymb. [ 1913 Webster ]

3. (Zool.) (a) The shaft of a feather. The rhachis of the after-shaft, or plumule, is called the hyporhachis. (b) The central cord in the stem of a crinoid. (c) The median part of the radula of a mollusk. (d) A central cord of the ovary of nematodes. [ 1913 Webster ]