1909.] NATURAL SCIENCES OF PHILADELPHIA. 317 



the body the Aviculariidae at least would seem to be considerably 

 modified. They might well be considered a modified branch which 

 has to great extent replaced spinning by burrowing. Few of them 

 construct true snares, and then only simple ones. Thus they might 

 stand in somewhat the same relation to the Araneae verse, as the 

 Ratitae do to the Carinatse among birds. 



While this hypothesis of the systematic rank of the Aviculariidae 

 may appear reasonable, we can hardly at the present time decide the 

 rank of the Liphistiidse and Atypidse, or indeed decide whether the 

 Theraphosse represent a homogeneous group. 



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