The collection of Alcyonarians made by the "Thetis" includes thirty-five species, of which thirteen are new,—a large proportion. When the specimens are arranged in systematic order, it is seen at a glance that the collection has a very definite character, namely, the proportionately large number of Isidae (e.g., six species of Mopsea, four new) and of Primnoidae (e.g.,five new spedes of Plumarella). These Isid and Primnoid colonies are extraordinarily beautiful, and their superficial resemblance to large fronds of Sertularians is striking. It is a matter for gratification that numerous specimens of some of the new species have been preserved, so that it was possible to make sure that one was not dealing with individual variations. Another feature of the collection is the frequent occurrence of encrusting colonies of Alcyonium (Erythropodium) membranaceum and A. reptans described by Kükenthal, which grow over Gorgonid axes in a very misleading fashion. It is not too much to say that an unprejudiced observer, who had not seen the real state of affairs exposed in unmistakeable cases, would describe these Gorgonid axes encrusted with Erythropoditlm as peculiar Axifera.