Type material of 20 species described in the genus Iulus by Paul Gervais (1837 & 1847) is still preserved in the collections of the Laboratoire de Zoologie-Arthropodes (Muséum national d’Histoire naturelle, Paris, France). This material, examined here, is related, except a single case, to the tropical millipede orders Spirostreptida and Spirobolida. For eight taxa represented only by females or immatures, it is impossible to class them below the level of family or even order: thus Iulus botta can be placed in Iulida; I. lagurus and I. leucopus to Spirostreptida; I. madagascariensis, I. philippensis, I. roseus and I. sumatrensis in Spirobolida. I. vermiformis is a mixing of Polydesmida and Spirostreptida. Five other taxa were reviewed in the recent past; thus Iulus bipulvillatus Gervais, 1847 is a junior synonym of Remulopygus javanicus (Brandt, 1841) (Harpagophoridae); I. chilensis Gervais, 1847, became Autostreptus chilensis (Spirostreptidae); I. corallinus Gervais, 1847, became Trigoniulus corallinus (Pachybolidae); I. haitensis Gervais, 1847, became Haitibolus haitensis (Rhinocricidae); and I. palmiger Gervais, 1847 is a junior synonym of Narceus americanus (Palisot de Beauvois, 1817). The six re-maining taxa have never been reviewed; they enter into the following new combinations and synonymies: Iulus sublaevis (mislabeled «Chili») becomes Gymnostreptus sublaevis (Gervais, 1847) n. comb., with a new synonym Gymnostreptus microps (Porat, 1872) (Brazil); I. trimarginatus (Brazil) becomes Gymnostreptus trimarginatus (Gervais, 1847) n. comb. (Spirostreptidae); I. verreauxii (Tasmania) becomes Amastigogonus verreauxii (Gervais, 1847) n. comb. (Iulomorphidae). I. striolatus («Amérique méridionale») becomes Neocricus striolatus (Gervais, 1847) n. comb. (Rhinocricidae) and is very close to Neocricus instabilis (Carl, 1941) n. comb. (Colombia); I. Eydouxii (Vietnam) becomes Eucarlia eydouxii (Gervais, 1847) n. comb., and is a senior synonym of Eucarlia charactopyga Attems, 1938 (Pachybolidae) n. syn.; I. spinicaudus (Southern India) becomes Carlogonus spinicaudus (Gervais, 1847) (Harpagophoridae) n. comb., and may be a senior synonym of Carlogonus subvalidus (Carl, 1941).
Myriapoda, Diplopoda, Gymnostreptus, Amastigogonus, Neocricus, Eucarlia, South America, Tasmania, Vietnam, India.