Palaeozoic Arachnida of North America. 41 



small, round depressions which evidently are the moulds of what 

 have been granules. The second has two longitudinal ridges and 

 two rows of depressions ; the third two ridges and one row of 

 depressions. The genital opercula, representing the first abdominal 

 sternite, are round. The basal plates of the comb, representing 

 the second sternite, have the shape of segments of a circle wdth 

 the curve directed posteriorly. The next or third sternite (usually 

 called the first) is the longest. The lines between the sternites 3, 

 4 and 5 are straight, while the anterior edge of the seventh sternite 

 is slightly recurved. Superimposed over the sternites are visible 

 the tergites. There are two parallel rows of round depressions 

 extending over the posterior three-fourths of the seventh sternite. 

 The ventral surface of the caudal segments shows two longitudinal 

 sulci, to which is added in the first caudal segment a transverse 

 row of depressions and in the third a median longitudinal sulcus. 



It may seem strange that the abdominal sternites are not separated 

 from each other like the tergites. One would naturally expect that 

 to be so, since this is the rule in recent scorpions. Two explanations 

 may be given to the fact, that the sternites of extinct scorpions are 

 not separated from each other by intersternal membranes. Either 

 the sternites were so long that they overlapped each other under 

 normal conditions in non-gravid females, or the ventral surface of 

 the abdominal segments was soft without hardened plates representing 

 sternites. In the first case we should expect to see double lines 

 separating each segment and that being so, that the anterior line would 

 represent the anterior edge of the posterior segment, while the posterior 

 Hne, the posterior edge of the anterior segment. I do not know 

 American Palaeozoic scorpions which would show such double lines 

 and assume therefore that the ventral surface of the third to sixth 

 abdominal segments was soft. It is different in the case of the se- 

 venth segment. This segment had evidently a strongly chitinized 

 sternite as evidenced by the presence of depressions. The pleura 

 may be seen on each side of the abdomen on the ventral surface of the 

 specimen superimpressed over the segments of the abdomen. 



The sternum is pentagonal. The mandibles, preserved only on 

 the obverse of the nodule, are egg-shaped, chelate ; their basal joint 

 is lost. The coxa of the palpus is not visible, and of the trochanter 

 only the distal end is preserved. Femur is 5.5 mm. long, patella 

 5.5 mm. long and scarcely wider than the femur, tibia with finger 

 7.0 mm. long. The movable finger (the tarso-metatarsus) is almost 

 twice as long as the hand, if both are measured in the line of contact 

 of the two fingers. 



