64 



A lexander Petriinkevitch, 



from each other and from the anterior edge by about their diameter. 

 The mandibles or chelicera are unusually large, but only the basal 

 joint visible, so that it is not possible to decide whether the fang was 

 movable upward and downward as in recent forms, or inward and 

 outward as in true spiders. The former is, however, more probable 

 since it is the rule in all recent pedipalpi. 



Fig. 23. Fig. 24. 



Figure 23. — Geralinura gigantea n. sp., from the Upper Coal Measures, 



Braidwood, lUniois, holotype, U. S. N. M. No. 37976, ventral surface, 



showing arrangement of coxae. Figure 24. — Same, dorsal surface. X y 



The abdomen is rounded in front, gradually narrowing posteriorly. 

 The pleura are well visible and Were soft and entire, the irregular 

 segmentation appearing in the specimen being due probably to arti- 

 ficial folding. The second to fifth abdominal tergites show clearly 

 the round attachment points of the dorso-ventral muscles, one pair 

 in each segment. On the ventral side one can see only ten sternites. 

 Of these the first, corresponding to the first and second segments, 

 is by far the largest and has a semicircular shape. The second sternite 

 has the shape of a segment, its posterior edge being procurved. Im- 

 pressed on it we see the bean-shaped genital opening. Only the an- 

 terior edge of the sternum is preserved and this is peculiar in its 

 structure inasmuch as it has articulation surfaces not only for the 

 pedipalpi, but also for the coxae of the first pair of legs. The pedi- 



