This chapter presents information on alkaloids of unclassified and unknown structure. The chapter presents a list on plants and their contained alkaloids. The structure of ankorine alkaloid has been revised on the evidence that none of the four possible synthetic racemic forms represented by the earlier structure is identical with the natural alkaloid. The chapter discusses camptothecine, Cannabis sativa L., dendrobine, Fagara xanthoxyloides Lam (Rutaceae), hippodamine, Oncinotis nitida Benth (Apocynaceae), and others. The Catha edulis Forskal (Celastraceae) alkaloid previously named cathidine has been shown to be a mixture comprised of a polyalcohol esterified with different amounts of acetic, benzoic, trimethoxybenzoic, evoninic, and nicotine acids. Reductive hydrolysis generates a polyalcohol that on acetylation provides an octa-acetate identical with that similarly obtainable from evonine. The report of the chemical study of the Myrrha octodecimguttata Coccinellidae contains the isolation of a new alkaloid, myrrhine (C13H23N liquid), and a review of the relationship that exists among the alkaloids that have been isoated from a number of arthropods—namely, coccinelline, convergine, hippodamine, and propyleine. © 1977 Academic Press, Inc.