ANCESTRAL Sl'lDERS AND TIIEIK HABITS. 



455 



Liphistius,^ and foi" this reason assigns it to his own family of Liphis- 

 tioidse.- 



Among the oldest fossil spiders, and probably the oldest in America, is 

 Arthrolj'cosa antiqua, from the Coal measures of Illinois, described by 

 Mr. Harger.* As the horizon in which this fossil was taken 

 . ^^. is synchronous with that of the argillaceous slate of upper 

 Spider Silesia in which Protolycosa was discovered, this American spi- 

 der has the distinction of being one of the oldest as yet known 

 to science. Its true determination is therefore a matter of great impor- 

 tance. The aranead has generally been recognized as a type of a new 

 family, Arthrolycosidaj, as first established by Mr. Harger. Professor 

 Scudder placed the family at the beginning of the oi"der Anthracomarli. 

 The supposed forcipulate character of the mandibles was considered suffi- 

 cient evidence to overcome the otherwise general resemblance to the Ter- 

 ritelarise, but this characteristic now ap- 

 pears to be without sufficient warrant. 



Professor Scudder'* made a reexamina- 

 tion of the type in 1884, and decided 

 against the forcipulate character of the 

 palps as described by Harger. More re- 

 cently Prof. Charles E. Beecher has made 

 a thorough study of the type specimen, 

 after cleaning it and exposing the append- 

 ages by removal of the superincumbent 

 matrix. After noting the differences which 

 the study of the specimens under these con- 

 ditions developed. Professor Beecher con- 

 cluded that on account of these important pi^. ggi fossU spider Arthrolycosa antiqua. 



differences it seems necessary to (After Beecher., ^^'':- ^^■'^^f^^J.f' 



same, viewed from the front. i.^fterBeecner.) 



exclude the genus from the order 



Authracomarti.' The marked resemblance between the ancient 

 Avicularidffi and the fossil seemed to suggest that Arthrolycosa 

 is entitled to a place in the suborder Tetrapneumones, among the Terri- 



FlG. 382. 



Arthro- 

 lycosa 

 antiqua. 



1 " Om en afvigende Slaegt af Spindlernes Orden." J. C. Schiodte. Natur historisk Anden 

 Raekes andet Bind Tidskrift, 1846-9, Bd. II., Rak. 2, page 617, sq. Thorell's reference is wrong, 

 a typographical error doubtless, making pages 6-7 for 617. As I count, he also errs in the 

 order of length of legs, which is 4, 3, 2, 1, instead of 4, 2, 3, 1. There is, however, but a frac- 

 tional difference between third (171;' lin.) and second (175'^), and this does not change the 

 force of the inference. The species is Liphistius desultor; female. Haljitat, Piiiang Island. 



^ European Spiders, page 222. 



=> American Journal of Science, 1874, Vol. VII., pages 219-223. 



* Proc. Amer. Acad. Arts and Sci., Vol. XX., 1884, page 1-5, " A Contribution to our 

 Knowledge of Paleozoic Arachnida." 



5 Note on the Fossil Spider Arthrolycosa antiqua Harger, by Charles E. Beecher. .\nier. 

 Journ. of Science, Vol. XXXVIII., 1889, page 219. 



