Later, Brauner obtained samples of the substance referred to as didymium. The name "didymium" also was retained in mineralogical texts. Welsbach named them praseodidymium (green didymium) and neodidymium (new didymium). This row would begin with a trivalent lanthanum, a teravalent cerium, and a pentavalent didymium. He theorized in 1874 that the element didymium consisted of two elements. The name "didymium" continued to be used in the rare earth metal industry. For example, "Squamuloderma nullifila" is actually a species from the genus "Didymium". He was right about lanthanum's being an element, but not about didymium. The species "Didymium sturgisii" is named in his honor. Some astronomical filters similarly use didymium in heavier concentration. The metals that formed these oxides were thus named "lanthanum" and "didymium". The rare-earth mixture didymium, previously believed to be an element, partially consists of neodymium(III) oxide. Welsbach separated didymium into praseodymium and neodymium. Didymium was discovered by Carl Mosander in 1841. He concluded that didymium was actually a mixture of two rare earth elements.