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ho). Fam. IV. THOMISIDiE [= Laterigradse nob. 



ad max. part.] 



Vid. Thor., On Eur. Spid., p. 169 et seq. 



(Pag. 410). I. THOMISUS [= Xystictts (C. Koch) 1835 + Corin- 



rachne Thor. 1870 + Di<ea Thor. 

 1870 + Misumena (Latr.) 1804]. 



On these genera see Thor., On Eur. Spid., p. 183—186. 



Some species belonging to the genus Xystims C. Koch, namely 

 X cristatus (Clerck), A', bifasciatus Koch, X. vlmi (Hahn) etc., 

 which greatly resemble each other in form and colour, constitute a 

 group, the synonyms of which present considerable difficulties. In 

 the older writers, including Walckenaer, the specific names crista- 

 tus, ciaticus etc. are without doubt collective denominations for seve- 

 ral different species. On the other hand Hahn and C. Koch have 

 described as specifically different several of these forms, which howe- 

 ver are often difficult to recognize with certainty, because these 

 authors almost exclusively gave their attention to differences of colour, 

 and neglected to study the organs of copulation, which probably 

 alone can offer sure and evident marks of distinction in these spi- 

 ders. The difficulty is considerably increased by the circumstance, 

 that the two sexes are very dissimilar, so that there is great risk of 

 error in determining which forms belong to each other as male and 

 female of the same species. As the males are comparatively easy to 

 distinguish, it seems most reasonable in the identification of species 

 in the first place to pay attention to them, especially as already 

 Blackwall, Westring, Ohlert and others have observed and duly 

 pointed out as particularly good marks of distinction the considerable 

 differences of form, which the males' palpi present in most of these 

 spiders. The females' vulvae indeed also exhibit peculiarities of form , 

 but these differences are not very conspicuous, and are moreover 

 difficult to figure and describe, so that the characteristic features of 

 that organ have been hitherto but little considered. The claivs do 

 not appear to me to offer any reliable assistance in the determina- 

 tion of the species; they differ greatly in form in the different sexes 

 (See Thor., On Eur. Spid., p. 185), and the number of teeth with 



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