A new genus, Ambicholestes, of concholestid Siphonoecetinae is described. Caribboecetes Just, 1983 is re-diagnosed to encompass C. barbadensis Just, 1983 (type species), C. jenikarpae Just, 1984a, C. intermedius Just, 1984a and, tentatively, C. pterycornis Just, 1984a only. Caribboecetes crassicornis Just, 1984a, C. magellani Just, 1984a and C. squamiferus Just, 1984a are transferred to Ambicholestes, together with six new species from Australia: A. cygnatratus, A. poorei, A. trilobatus, A. berentsae, A. thetis, and A. minutus. The three last mentioned species are placed in a new subgenus, Austrolestes. The main character distinguishing Ambicholestes s.l. from Caribboecetes is the presence in the former of unique, complexly lobate inner lobes of the lower lip. A possible stridulation organ involving coxal plate 2 and pereopod 2 is described for three species of Ambicholestes. A key to Australian Ambicholestes is provided. Ambicholestes squamiferus is recorded from Guam.