Palaeozoic Arachnida of North America. 125 



Architarhus rotundatus Scudder. 

 Plate VII, figs. 74—79, 81—83; text figs. 79, 80. 



A. rotundatus Scudder, Geol. Surv. Illinois, Vol. Ill, 1868, p. 568. 



= Geraphrynus carbonarius Idem, Mem. Boston Soc. Nat. Hist., 

 1890, p. 446, pi. 40, figs. I, 9, 10, 12. 



A. rotundatus Melander, Jour. Geol, Vol. XI, 1903, p. 181, pi. V, 

 fig. 2 ; pi. VII, fig. 2. 



=: Geraphrynus carbonarius Idem, Ibid., p. 181, pi. V, fig. 3; 

 pl. VII, fig. 3. 



There are altogether seventeen more or less well preserved spe- 

 cimens of this species distributed as follows : 



One specimen, No. 1116, the type specimen of A. rotundatus, in 

 the collection of the University of Illinois. 



Nine specimens, Nos. 1116, 37961, 37962, 37979, 37980, of which 

 several are under the same numbers, in the collection of the U. S. 

 National Museum. Of these No. 37961 was originally No. 1701 ab 

 of the Lacoe collection and is the type of Geraphrynus carbonarius. 



Two specimens in the Daniels collection. 



Two specimens in the Walker Museum of the University of Chicago. 

 Of these Nr. 9234 was identified by Melander as A. rotundatus, and 

 No. 9233 as Geraphrynus carbonarius. 



Three specimens, Nos. 185, 186, 187 in the collection of the Peabody 

 Museum of Yale University. 



All specimens come from the same locality and have the same 

 structure, although their size varies from 12 to 24 mm. Hansen and 

 Sorensen are decidedly wrong when they suggest that the three 

 specimens of Geraphrynus carbonarius represented by Scudder in plate 

 40, figs. I, 10, and 12 " belong to at least two different genera, per- 

 haps even to different families or orders " (p. 139). Scudder has cor- 

 rectly recognized the specimens as belonging to the same species and 

 if he had cleaned the type specimen of A. rotundatus of the heavy 

 layer of kaolin with which it was covered he would have undoubtedly 

 recognized the identity of his two types. 



A photograph of the type specimen of Architarbus rotundatus after 

 I have carefully cleaned it, is given on plate XII, fig. 74. Pho- 

 tographs of the obverse and reverse of the type specimen of Gera- 

 phrynus carbonarius are given on plate XIII, fig. 80. There is no 

 difference whatever in the proportions or the details of structure. The 

 first is 20.0 mm. long, the second 19.0 mm. Specimen No. 37979 of 

 the U. S. National Museum is reproduced on plate XII, fig. 72. It 

 is 12.0 mm. long. The better specimen in the Daniels collection is 



