36 Alexa)i(kr Petrunkevitch, 



KEY TO GENERA OF NORTH AMERICAN CARBONIFEROUS 

 SCORPIONS 



1. Seventh abdominal tergite similar to the preceding ones, 8 th 

 similar to the 7th of recent scorpions. 



Mazonia 

 + seventh abdominal tergite as in recent scorpions. Post- 

 abdomen with 5 segments 2 



2. Coxae of 3d pair of legs abutting against the sternum, those of 

 4 th pair against the genital opercula. 



Palaeohuihus 

 + coxae of 3d and 4th pair of legs abutting against the sternum 

 (coxae of Trigonoscorpio and Eoctonus not known but 

 presumably of this type) 3 



3. Cephalothorax triangular ; anterior border more than 4 times 



narrower than the posterior one. 



Trigonoscorpio 

 + cephalothorax never as narrow in front 4 



4. Post-abdomen very short and slim. 



Palaeopisthacanthus 

 + post-abdomen normal 5 



5. Hand short and wide, with short fingers. 



Eoctonus 

 + hand narrow, fingers very long. 



Eoscorpitis 



DESCRIPTION OF NORTH AMERICAN PALAEOZOIC SCORPIONS 



Family Eoscorpionidae. 



Genus Eoscorpius Meek and Worthen. 



New definition. Sternum pentagonal. Cephalothorax with more 

 or less parallel sides, never conspicuously narrowed in front. Mid- 

 dle eyes either removed from the anterior edge of the cephalothorax 

 at least Vs its length, or if placed close to it then the edge itself 

 straight. Cauda normal. Hand narrow with very long fingers. 



The type species, E. carhonariiis, resembles very closeh' the Euro- 

 pean E. dunlopi (Pocock) and E. sparthensis Baldwin and Sutcliffe, 

 but is considerably smaller. Pocock rejects the genus Eoscorpius in 

 favor of Anthracoscorpio since the characters of the former are not 

 sufficiently known. A comparison of the type with E. typicus and 

 E. danielsi shows, however, that these species are very closely related 

 to the type species, although sufficiently distinct not to be placed 

 under the same species. In fact, E. typicus could have been regarded 



