5G Alexander Petrunkevitch , 



tween scorpions and Pedipalpi, not in the sense X\i2X ^l azonia was an 

 ancestor of Pedipalpi, which it certainly was not, but that it represents 

 a tendency in the same direction of diminution in size of the last 

 segments. 



To the description of Meek and Worthen may be added that in 

 front of the cephalothorax are visible the impressions of the first 

 joints of the mandibles, but it is not possible to decide whether the 

 mandibles were chelate or retroverte. Pocock thinks that a separate 

 group should be created for Mazonia, and I fully agree with him on 

 this point. But the specimen is too fragmentar}^ for that purpose and 

 this is the reason why I have retained the genus Mazonia in the order 

 of scorpions where it has been originally placed. The specimen was 

 found in the Pennsylvanic (Lower Allegheny) of Mazon Creek, Illinois. 

 At present it is in the collection of the University of Illinois, at 

 Urbana, Illinois. 



Scudder has described two other specimens of Mazonia ; the one 

 he calls M. acadica, the other Mazonia sp. (cf. Geol. Surv. Canada, 

 Vol. II, 1895, pp. 62—65, pl- V, figs. 4—9). I have carefully examined 

 both specimens but am not able to find sufficient characters to place 

 them among the arachnids. They represent what may have been an 

 arthropod, but nothing more definite can be said about them. 



ORDER PEDIPALPI 



With the exception of the recent family Scbizonotidae in which 

 the two last thoracic segments, fused together, are movably jointed 

 to the anterior part of the cephalothorax, the head is completely 

 fused with the thorax. The abdomen, composed of eleven to twelve 

 segments, is never broadly joined to the cephalothorax. The 

 chelicera always retroverte ; the pedipalpi powerful, raptorial, retro- 

 verte or chelate. The first pair of legs modified as tactile organs. 

 All five post-oral appendages with a patella.^ Two pairs of lungs 



^ Kraepelin is certainly in error when he calls the patella of the pedipalp, 

 tibia, and the tibia, hand. The muscular system of the patella is charac- 

 teristic of this joint. But whereas in scorpions the chelate pedipalp hand 

 is formed by the tibia with its process as immovable finger and the tarso- 

 metatarsus as movable finger, the immovable finger of Pedipalpi is usually 

 formed by the process of the patella. There is often a line of separation 

 between the tarsus and metatarsus as shown in text figure 17. 



