128 PrGceedhigs of Indiana Academy of Science 



assigns eight species, four occurring in Europe and four in America. 

 No species are found to be common to both continents. From these 

 facts Petrunkevitch drew the two following conclusions: (1) "that the 

 Carboniferous arachnological fauna of North America is distinct from 

 that of Europe and developed along somewhat different lines," and (2) 

 "that both faunas have more similarity with recent faunas of tropical 

 countries, than with such of the same locality.'"' The following outline 

 brings out Petrunkevitch's classification very clearly: 



Order Scorjriones. 



"Head completely fused with the thorax. Abdomen twelve-jointed, 

 the last five somites forming the so-called cauda or post abdomen, 

 considerably narrower than the anterior seven. Telson with a poison 

 gland and sting. Chelicerae three jointed, chelate. Pedipalpi six-jointed, 

 chelate, powerful. Coxae of first and second pair of legs with maxillary 

 lobes. Abdominal tergites and sternites heavily chitinized connected 

 laterally with each other by means of a .-^oft chitinous cuticle capable of 

 considerable distension. Post abdominal segments without pleural mem- 

 branes, their sternites and tergites comiiletely fused in each segment. 

 First sternite represented by the genital opercula, second sternite by 

 the basal joint of the comb. Four pairs of stigmata leading to lung- 

 books in third to sixth sternites, one pair to each sternite. Anus with- 

 out operculum at the end of the twelfth abdominal segment, ventral to 

 the poison gland. Two middle eyes and two to five pairs of side eyes 

 en cephalothorax, seme recent species completely blind. All recent scor- 

 pions are viviparous." 



Sub-order — Apoxijdopd ( Silurian) . 



Tarsi terminating in a sharp point, without claws. 

 Family Palaeophonidae (T. & L. 1884). 



Genus Palaeoplionus (3 species, all European.) 



Genus Pvoscorpmn (1 species, American.) 

 Sub-order — Dionycho]wda. 



Scorpions with two claws at the end of each tarsus (includes Po- 



cock's Lobosterni and Opisthosoma). The families of this 



sub-order are based on the structure of the coxae and not upon 



the shape of the abdominal sternites. 

 Family Isobnlhidae. Coxae of the fourth pair of legs abutting 



against the genital opercula. 



Genus laobiiffms (1 species, European). 



Genus Eobutlms (2 species, European). 



Genus Palaeabiithus (1 species, American). 

 Family Cydophthalmidac. Normal arrangement of coxae, sternum 



pear-shaped. 



Genus CyclopJithabiius Corda, 1835 (2 species, European). 



Genus PalaeonmchuH Pocock, 1911 (2 species, European). 



Genus ArcJmeoctonus Pocock, 1911 (1 species, European). 



''Petrunkevitch, A.-- MonoK'i-aph of the Terrestrial Paleozoic Aiach. of North Amer- 

 ica, Trans. Conn. Acad, of Aits and Sci., Vol. 18, )i. 28. 



