Palaeozoic Arachnida of North America. ' 55 



" The abdomen measures about 33.65 mm. in length, and near 

 13.7 mm. in breadth, as seen in its crushed condition. There appear 

 to be at least seven segments, with just space enough between the an- 

 terior, or seventh one seen, and the cephalothorax, for an eighth one. 

 Excepting the posterior one (which is ornamented on the central 

 region of the posterior half with small granules, some of which are 

 arranged in longitudinal rows), these segments seem to be smooth. 

 The exact outline of the posterior segment is not clearly seen in the 

 specimen. ... In clearing away the matrix, its posterior margin was 

 seen to be truncated, as if for the attachment of a stout tail, but 

 trying to work away more of the matrix, its margin was broken away 

 so that it does not now show the truncated edge so clearly as represen- 

 ted in the figure. Its lateral margins are somewhat flattened No 

 traces of the tail are preserved, the concretion being too small to have 

 included it. 



" Just in front of the cephalothorax, extending obliquely forward, 

 and outward to the right, a part of apparently one of the palpi is seen 

 in the matrix. Unfortunately, however, its terminal portion is 

 broken away. It seems to have been long and slender. At the inner 

 end, there appears to be but one, though there may be two, short 

 joints, and beyond these, there are two long slender ones. . . . An 

 obscure impression of a part of one of the legs is also seen farther 

 back, extending out from the right side." 



As will be seen from the above quotation. Meek and Worthen 

 suppose that the abdomen may have been composed of eight segments, 

 in which case, if Mazonia is a scorpion, the cauda must have been 

 only of four segments, since the number of segments in all known 

 scorpions is twelve. On examining the specimen I too came to 

 the conclusion that the last segment shows all semblance of the 

 seventh abdominal tergite of a normal scorpion. There is also 

 no doubt that behind the cephalothorax is a segment. It may 

 be clearly seen even on the photograph. The two alternativs 

 would be therefore that tliis segment represents the last thoracic 

 segment which remained free as is the case in Solifugae and 

 Palpigradi or the pregenital segment characteristic of embryos. 

 Neither of these alternatives, however, finds a support in the 

 structure of either extinct or recent scorpions. One could rather 

 conceive a scorpion with six abdominal and six caudal segments, 

 as that Would be more in agreement with some Eurypterids 

 and Xiphosura. Perhaps Mazonia had after all no distinct sepa- 

 ration between abdomen and cauda, and the last four segments were 

 small. In that case it could be considered a transitional form be- 



