Palaeozoic Arachnida of North America. 63 



dominal segment same width as cephalothorax, but the constriction 

 between cephalothorax and abdomen is well visible on the ventral 

 surface. Segmentation of abdomen indistinct, neither the tergites, 

 nor the sternites being preserved. Whip lo mm. long. Pedipalpi 

 heavy, their coxae meeting in the median line, longer than wide, with 

 a distal internal process. The trochanters wider than long, the femora 

 with a process at inner edge. The patellae curved, their distal end 

 possibly representing the immovable finger. Tibia and tarso-meta- 

 tarsi lost. The first coxae as in recent Thelyphonidae. The femora 

 long and thin, the rest not preserved with exception of the proximal 

 end of the patellae. First femur 8.5 mm. long. Second femur much 

 thicker and only 1.75 mm. long. The sternum 3.00 mm. long, pointed 

 behind. The coxae of the second pair conical, those of the third pair 

 with parallel sides, diverging in front, contiguous at posterior end. 

 Coxae of fourth pair contiguous, rectangular. It is doubtful whether 

 the fourth leg is as thin as it appears, more probably it was as heavy 

 as the second and third, this being indicated by the width of the proxi- 

 mal fragment of the femur. 



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



Geralinura gigantea n. sp. 

 Plate V, figs. 23—25 ; text figs. 23—26. 



The holotype of this species is in the collection of the U. S. National 

 Museum under the number 37976. The obverse shows the cephalo- 

 thorax, five segments of the abdomen, pedipalpi, chelicera and frag- 

 ments of legs ; the reverse, the palpi, chelicera, coxae of all legs, 

 abdomen, almost complete first right leg and several joints of the 

 remaining legs. The whip is not preserved. 



Total length 21.0 mm. The flat, excellently preserved cephalo- 

 thorax is 6.3 mm. long and 4.5 mm. wide ^/a from anterior edge, 

 i. e., in its widest place. Anteriorly the cephalothorax is truncated, 

 the posterior edge is very slightly recurved, almost straight and about 

 twice as wide as the anterior edge. Immediately behind the widest 

 place there is a conspicuous median ridge sloping posteriorly and 

 anteriorly where it goes over gradually into curved grooves running 

 towards the deep lateral grooves. The lateral grooves themselves 

 begin at anterior edge and run parallel to the sides of the cephalo- 

 thorax. They represent the moulds of the lateral crests as in recent 

 forms, and the enlarged portion of their posterior end may have been 

 the place where the lateral eyes were in the living specimen, but no 

 trace of the lenses is left. The middle eyes are oval, small, separated 



