24 Alexander Petrunkevitch, 



is true of tlie scorpions is true to a still greater extent in some of the 

 other orders. Thus the genera and species of recent spiders are 

 based almost entirely on such characters as will never be found 

 preserved in Carboniferous forms. What value then have the genera 

 and species of that extinct fauna ? We may safely say that in the 

 majority of cases the species of Carboniferous arachnids would have the 

 value of genera in a recent fauna. Many genera would be regarded 

 as families and some families as suborders. If therefore, basing our 

 judgment on the preserved characters, we should come to theconclusion 

 that a certain Carboniferous European species is identical with a 

 North American one, we would be judging from insufficient evidence. 

 Fortunately such cases do not exist and the Carboniferous species 

 of North America are clearly distinct from those of Europe. 



Of the extinct orders the Haptopoda, represented by a single 

 species Plesiosiro madeleyi, are known only from Europe, and the 

 Kustarachnae, represented by three species of a single genus, only 

 from North America. The orders Anthracomarti and Phalangio- 

 tarbi, both extinct, are represented in both countries. The order 

 Anthracomarti is much richer in Europe than in North America. 

 Its first family, Anthracomartidae, is represented there by 4 genera 

 with 12 species ; of these the genus Anthracomartus is represented 

 in Europe by 9 species as against 2 species in North America. It 

 is the only genus of the family so far discovered in North American 

 deposits, and it is interesting to mention that neither of the two 

 species has been found at Mazon Creek, the A. trilobitiis being a 

 common arachnid from Arkansas in strata somewhat older and 

 A. triangularis being represented by a single specimen from the 

 Joggins Mines in Nova Scotia from Leds younger than those of Mazon 

 Creek, The second family, Eophrynidae, is represented in Europe 

 by 13 genera with 16 species, in North America by 3 genera with 

 4 species. Of these the genera Areomartus and Trigonomartus are 

 American, while the two species which I have placed under Pocock's 

 genus Trigonotarbus may in reality be representatives of a separate 

 genus. Among the Phalangiotarbi the family Heterotarbidae with 

 its single species Heterotarhus ovatus is known onl}^ from this country. 

 The family Phalangiotarbidae is represented in Europe by a single 

 genus and species, Phalangiotarhus suhovalis, which does not occur 

 in North America, as against 3 genera with ^ species in this country. 

 The family Architarbidae is represented in North America, by the 

 genera Opiliotarbus and Architarhus, the first with i, the second 

 with 3 species. In Europe it is represented by Architarhus alone, 

 of which there are known 5 species. 



