Palaeozoic Arachnid a of North America. 



127 



segments was not thickened. The pleura appears as a heavy ridge 

 along the sides of the abdomen. In life it must have been soft 

 and not segmented, the cross lines being due to folding. In places 

 the pleura is chipped off and under it is exposed the edge of the ab- 

 domen. The anus is visible on both the reverse and obverse. In 



■^t'j. 



Fig. 80. 



Figure 80. — Architarbtis rotiindatiis Scudder, specimen No. 185 ventral sur- 

 face as it appears on the nodule with this difference, that the left fourth leg 

 in the specimen is curved inwardly and lies under the abdomen. X -^- 



the latter it appears in the tenth tergite close to the pleura, and 

 is surrounded by a heavy wall. The surface leaves no doubt that 

 the anus was protected by a round operculum, placed ventrally. 

 The cephalothorax is smooth, but the abdominal tergites are 

 clearly punctate. 



The number of sternites is apparently only seven The first 

 sternite is very large, triangular, smooth. It hcis a deep transverse 

 groove representing probably the mould of a ridge or movable plate 



