From the Jaseur Bank, off the Brazilian coast at 20º 30' S - 35º 50' W, were collected a few specimens of one of the less known species of the Heteropoda: Firoloida lesueuri (d'Orbigny). A detailed anatomical description follows aiming at the elucidation of some obscure points in the litterature on the subject and at showing the identity of most of the previously described "species" of the genus Firoloida. Special care was taken with the study of the nervous system of which most of the descriptions found were discordant. The author arrived at the conclusion that the pleural ganglia are either missing of fused to the cerebral ganglia, that the supraintestinal ganglion (left parietal ganglion) is present in the posterior region and is close to the subintestinal or right parietal ganglion, being both located near the rear end of the body. The innervations are described and discussed as well as the fusion of extensive tracts of the connectives. The present material is shown to be identical to F. kowalewskyi, well described by Vayssière and Tesch; F. desmaresti (Lesueur 1817) is shown to be undistinguishable from F. blainvilleana and F. gracilis. F. aculeata and F. gaimardi are here considered as "nomina nuda". F. liguriae Issel 1907 is admitted as separate species in spite of its insufficient description and, finally, F. vigilans (Troschel 1855), unsatisfactorily described from only one specimen is perhaps a valid species. A table is presented to show the slight differences between the 4 species which are undoubtedly very similar. F. desmaresti is found only in the Atlantic north of the line and a few points south and close to it as well as in dependent seas, while F. lesueuri is common to the south Atlantic, south Indie and south Pacific oceans, extending north only up to the Azores Islands. F. liguriae is from the south western Atlantic. ?F. vigilans would be an endemic species from Messina (Mediterranean).
