Tertiary Spiders and Opilioruds. 219 



in absence of definite data it seems wiser to limit the discussion of 

 homologies to somites the presence of which can be always demon- 

 strated. The same holds true of Xiphosura. 



CLASSIFICATION IN ARANE.^. 



Let us now proceed in detail with the discussion of the problem 

 of classification in spiders and especially with that of identification 

 of extinct species. Lest much of what I have said may seem to 

 be unsupported by facts, arbitrary and attributable rather to per- 

 sonal shortcomings of the author than to poor preservation of the 

 material itself, I shall give two examples and submit these to an 

 exhaustive analysis so that the reader may form a judgment for 

 himself. The spiders which I choose for this purpose, Parattiis 

 resurrect lis and Titanoeca ini^cnna, are fairly well preserved. 

 Both belong to the sub-order of Arachnomorphas or True Spiders, 

 characterized by the direction of the axis of articulation of the 

 chelicerae, the presence of well developed maxillary lobes and the 

 possession of a single pair of lungs and of a single (or of a pair) 

 tracheal spiracle. Neither of these characters can be determined 

 from an examination of the specimens in question, but the combi- 

 nation of other characters, the general appearance, the size, the 

 proportion of the legs, the "tout ensemble" so to say, makes a 

 mistake impossible. So far, so good. 



The first sub-division of True Spiders is based on the presence 

 or absence of a cribellum in front of the spinnerets and of a cala- 

 mustrum on the fourth metatarsus. The Family Attid?e, to which 

 according to Scudder who established the genus Parattus for 

 three species of Tertiary Spiders that genus belongs, comes under 

 the division Ecribellata!. The absence of a cribellum and calamis- 

 trum in recent spiders may be ascertained without difficulty, but 

 only with the aid of a lens. Moreover, the calamistrum can be 

 seen only in a certain position of the leg. How much of these 

 structures may have been preserved in extinct spiders? Spines 

 and hair are well preserved in some specimens. Spinnerets, as a 

 rule, are not nearly as well preserved. In Parattus rcsurrectus 

 one can see with the aid of a good binocular dissecting microscope 

 at a magnification of about 60 diameters simple brown hair on the 

 spinnerets and similar hair and spines on all legs. No cribellum 

 and no calamistrum are visible. In absence of traces of these 



