In 1882, Dr. Geo. H. Horn (Trans. Amer. Ent. Soc., x., 1882-83; Monthly Proc., Feb. 10, 1882, p. ii.) exhibited drawings illustrating the anatomy of _Platypsylla_ and _Leptinus_, and showed that a close relationship exists between these genera. Later, in his "Notes on Some Little Known Genera and Species of Coleoptera" (Trans. Amer. Ent. Soc., x., 1882-83, pp. 113-126, pl. v., 114-116), he reviews the characters, and explains and illustrates the anatomical details. The differences he points out between his observations and those of Le Conte are more particularly in the mandibles. In connection with this paper he also describes and illustrates the structure of Leptinillus, which he separates from Leptinus, and demonstrates their close relationship with Platypsyllus. In 1883, Le Conte and Horn, in their "Classification of the Coleoptera of North America" (Washington, Smithsonian Institution, 1883), give (pp. 13-15) a full description of the family characters, a little modified from Le Conte's first description, but sustaining his views on the systematic position of _Platypsyllidæ_. In 1883, Alphonse Bonhoure (Ann. Soc. de France, 1883; Bull, des Seances, p. cxxvi.) exhibited drawings and specimens of _Platypsyllus castoris_ found in the _Departement des Bouches du Rhone_. In 1884, Edm. Reitter, in "_Platypsylla castoris_ Rits. als Vertreter einer neuer europaischen Coleopteren-Familie" (Wiener entom. Zeit. iii., 1884, pp. 19-21) gives a lengthy description of the species with special regard to the sexual differences. He shows that the European insect is not specifically distinct from the American form, but he does not express an opinion on the position of the family among the Coleoptera. In the same year, Bonhoure (Ann. Soc. Ent. de France, 1884, pp. 143-153) more fully records its discovery on _Castor fiber_ taken in the Petit-Rhone. It is a question whether this European beaver, now quite rare, is distinct from ours. He gives a very good review of the subject, with a plate of the most important details, after Horn, and he fully indorses the coleopterological position of the insect. In the same year Ritsema (_Tijdschrift voor Entomologie_, 1883-84, lxxxvi.) refers to Bonhoure's discovery of _Platypsylla_ in France, and corrects Reitter in some unimportant details. In 1885, Reitter, in "_Coleopterologische Notizen_" xiii. (Wiener entomolog. Zeit., vol. iv., 1885, p. 274), answers Ritsema's criticism. In the same year, Dr. Friederich Brauer, in his masterly "Systematisch-zoologische Studien" (Sitzh. der Kais. Akad. der Wissensch., xci., p. 364), speaks of the relationship in the thoracic characters between Mallophaga and Coleoptera as illustrated by Platypsyllus, by inference admitting the coleopterous nature of the latter, but recognizing that it has mallophagous affinities.