22 Alexander Petrunkevitch , 



does not seem to me to be con\nncing. The specimen of Geralinura 

 gigantea in the possession of the U. S National Museum shows 

 a lamelUbranch in the same concretion, yet there can be no doubt 

 that all species of Geralinura Were terrestrial arachnids. As Pro- 

 fessor Schuchert has pointed out to me, the impression of marine 

 animals on the same concretion with arachnids is probably due to 

 the fact that the dead creatures were washed from the land into 

 the sea where they became fixed in the mud with the other brackish- 

 water remains. The more or less frequent occurrence of ferns in 

 the same concretion with arachnids is due to the same cause and 

 points to the fact that such species lived in a moist climate. We 

 may further conjecture that it was a hot climate, since the majority 

 of living forms of the same orders are mainly distributed throughout 

 the tropical and sub-tropical zones. It is true that the recent re- 

 presentatives of Pedipalpi and especially of Solifugae are more 

 characteristic of dry regions, many of them being even true desert 

 forms; yet on the one hand, a change in climate may have brought 

 about a change in habits, and on the other, species are known which 

 still prefer wet regions. Thus I have found a Solifugid and ambly- 

 pygous Pedipalpi under bark of decaying tree trunks on the western 

 coast of Chiapas where the yearly rainfall is very high and the countr 

 rich in tropical rain forests. Some species of scorpions and many 

 Theraphosid spiders are found in quantities in the lowest parts of 

 tropical jungles. 



The similarity in structure between extinct forms and recent 

 ones suggests that the food must also have been similar, consisting 

 of land animals belonging to the arthropods, possibly some arthro- 

 stracous crustaceans, and more certainly Palaeodict\'optera, Proto- 

 blattoidea, and arachnids. The Anthracomarti and Phalangiotarbi 

 must have been preying on very small invertebrates since their 

 mandibles were so Weak that no traces of them are left. It is not 

 impossible that some of them were phytophagous. The methods 

 of defense against enemies must also have been similar, since the 

 scorpions show a well-developed poison gland and the mandibles 

 of the Pedipalpi and Araneae were apparently of the same type 

 as those of recent forms. It might be supposed that the poison 

 apparatus developed for the purpose of killing the prey and not 

 for self defense, but the study of living arachnids show that they 

 avoid using their poison for that purpose. I have tried in vain to 

 find among the fossiles studied some evidence in regard to their 

 methods of reproduction. The distended abdomen of some scor- 

 pions and Pedipalpi is indicative of their being gra\-id females. 



