Having completed the examination of the Earthworms, brought home by the Sumatra-Expedition 1) and destined to be deposited in the collections of the Leyden Museum, I was surprised to find in the latter some specimens of tropical Lumbricina, hitherto not described. These specimens, being collected a long time ago by von Siebold, Kuhl & van Hasselt and Horstock, are not in a very good state of preservation (as was also the case with the worms from the Sumatra-expedition), and so I regret to be not able to give always so exact a description, as should be desirable. Before undertaking the description of the different species, it will be necessary to give some details about the history of the genus Megascolex, because there seems to exist a good deal of confusion concerning that generic title. The genus Megascolex has been based by Robert Templeton 2), in the year 1845, upon large worms found in the Alpine regions of Ceylon, which had each ring in the middle of its length dilated into a ridge, which carries on it, except in the mesial line of the back, minute conical mamillae, 100 in number, each surmounted with a minute bristle. The author gives some annotations concerning the anatomical structure of these worms, the situation of the pores on the back etc. and concludes that without any doubt they are closely allied to Lumbricus. About fifteen years after the publication of Templeton’s paper Schmarda 1) created a new genus Perichaeta, based on earthworms, also natives of Ceylon, characterized by having each segment surrounded in the middle by a circular ridge, which is beset over the whole circumference of the body by a row of bristles. In describing this new genus Schmarda mentiones also the genus Megascolex of Templeton, but unfortunately he seems to have misunderstood Templeton’s description, for he says, that the genus Megascolex is quite different from Perichaeta by having only a row of bristles on the back, whereas the only difference is that in Megascolex the bristles are wanting in the mesial line of the back. The same mistake is made by Grube 2), who in his classical work „Die Familien der Anneliden” erroneously characterizes the genus Megascolex by »Rücken mit borstentragenden Papillen bedekt (reihenweise längs den Seiten stehenden Borsten fehlen)”. He certainly has much contributed to the error finding its way also in other books; so Vaillant 3) in his table of the classification of the Earthworms repeats: »soies sur des papilles rassemblées a la partie dorsale”. The only author who calls the attention upon Schmarda’s mistake is Baird 4); he also examined the type-specimens of Megascolex coeruleus and could not find any characteristic difference between Perichaeta and Megascolex. His conclusion, that both genera are identical, I believe to be quite exact and consequently the name Perichaeta must be cancelled, while Megascolex has indisputable claims of priority. We must regret that Perrier 1), who afterwards has so much contributed to our knowledge of the genus Perichaeta not only has fallen into the same error above referred to, but moreover that he imputes Baird from having confused the genus Perichaeta with Megascolex (Rech. p. s. à l’hist. des Lombr. terr. Nouv. Arch. Mus. Hist. Nat. T. VIII, p. 153).