Firstly, it includes nine still-valid first descriptions of spider species. In the 19th century not unusually, a majority of "new species" had been previously described by other authors, because in contrast to the modern differentiation of species, the genital structures were not taken into consideration at that time. For that reason, smaller differences in the colourings and markings have possibly given rise to different species designations. At any rate, a sixth of the forms described by Hahn are still valid today. That Hahn was a good observer and gave exact descriptions is shown clearly by the example of "Eresus annulatus" (= "E. sandaliatus" (Martini & Goeze>, 1778)) and "E. cinnaberinus" (= "E. kollari" Rossi, 1846). After more than 150 years, arachnologists follow his separation of these taxa today again.