158 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



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or which is but dimly iUuminated, would seem to be less decided transition 

 than in the case of many other genera. Nevertheless, the facts at present 

 within possession of araueologists appear to indicate that the Tubeweavers 

 have secured no permanent rej^resentatives among our cave fauna, this 

 position being wholly occupied by members of the Retitelaria?. We have 

 thus iiresentcd the curious fact that the species which by natural tendency 

 appear to be best adapted to survive cavern conditions have been tlior- 

 oughly eliminated or excluded. 



