Palaeozoic Arachnida of North America. 9 



imposed structures were omitted from the drawing and where possible, 

 each surface was drawn separately. Wherever this was necessary, 

 special reference to it will be found in the text ; but to avoid the pos- 

 sible objection of misinterpretation or misconception, all specimens 

 drawn in text were photographed from the originals and are repro- 

 duced on the plates directly from the photographs. The photo- 

 graphing was done by Doctor R. S. Bassler of the U. S. National 

 Museum. 



The net results of the present investigation are as follows : (i) loi spe- 

 cimens including all types were studied and found to belong to 42 spe- 

 cies distributed over 25 genera ; of these, 24 species and 13 genera are 

 new to science ; (2) the diagnoses of old genera are corrected in accor- 

 dance with the new data obtained from the study of the types and 

 of specimens which undoubtedly belong to the type species ; (3) the 

 genus Eoscorpius was found to be sound and is retained in the system ; 

 the genera Hadrachne Melander and Geraphrynus Scudder were found 

 to be synonyms of Architarbus Scudder ; (5) the type of Geraphrynus 

 carhonarius was found to be in every detail identical with the type 

 of Architarbus rotundatus, the former name being, therefore, a syno- 

 nym of the latter ; (6) a representative of the order Solifugae hitherto 

 unknown to Palaeontology has been found in Protosolpuga carbonaria 

 n. gen., n. sp. ; (7) a new order Kustarachnae has been established for 

 the three species of Kustarachne. 



THE SYSTEM 



Although the class of Arachnida has received a good deal of 

 attention from zoologists and palaeontologists, there exists still 

 considerable divergence of opinion as to the essential characters 

 separating this class from the rest of the arthropods. The typical 

 forms such as scorpions and spiders have only 6 pairs of uniramous 

 appendages of which the first pair is praeoral. The segmentation 

 of the legs is also alike in the typical forms and shows the close re- 

 lation existing between them. This is also true of the Xiphosura 

 and Gigantostraca (Eurypterida) which are now usually placed in 

 the class of Arachnida. 



Yet under the influence of parasitism this character becomes more 

 or less obliterated and we find only 4 pairs of appendages in the 

 family Eriophyidae among the Acari. On the other hand Pycno- 

 gonida which are often classed as an order of marine Arachnida, show 



