46 Alexander PetriDikcvitcli, 



the longest tergite. Along the posterior edge of each tergite and on 

 the sides of the seventh tergite runs a row of small, round punctuated 

 depressions. The combined length of the three post-abdominal seg- 

 ments is 27 mm. Two rows of punctuated depressions, representing 

 the dorsal crests, are visible on the first and second post-abdominal 

 segments. The pedipalp is long and slender, hand with very long 

 fingers; length of femur 15 mm., patella 15 mm., tibia with finger 

 23.0 mm. Length of movable finger 17.5 mm. 



Specimen No. 130, showing also the dorsal side alone, is some- 

 what smaller ; the cephalothorax measures y.% mm. in length and 

 ii.o mm. in width. It is badly deformed. Only six abdominal ter- 

 gites are preserved. The right pedipalp is complete and the length 

 of its joints is as follows : femur 7.5 mm., patella 6.4 mm , tibia with 

 finger 13.5 mm. A few severed joints of three right and two left legs 

 are preserved, but it is not possible to identify them. It may be that 

 the specimen is a male or represents a different species, since the rela- 

 tive length of the palpal joints is difierent from that of the type 

 specimen. But the general appearance is much as in the type spe- 

 cimen and the preservation not sufficient to make of this specimen 

 a different species. 



Specimen No. 129 (PI. Ill, figs. 11, 12). The nodule containing 

 this specimen consists both of the obverse and the reverse, but the 

 latter is badly deformed. The obverse shows the cephalothorax 

 with the eyes, abdomen and one post-abdominal segment, mandibles 

 and parts of femora and tibiae of the legs. One complete pedipalp 

 is preserved on the reverse. The structure of the cephalothorax 

 which is 6.7 mm. long and 8.0 wide, is the same as in the type specimen. 

 The abdominal tergites increase gradually in length and have the same 

 sculpture as the type specimen. On the other hand the pedipalp is 

 more like that in specimen No. 130. The length of its segments is as 

 follows : femur 12.3 mm., patella 9.4 mm., tibia with finger 14.3 mm. ; 

 length or movable finger 9.2 mm. ; length of abdomen 18.0 mm. 

 Unlike the two preceding specimens the rock in which this specimen 

 is imbedded shows no signs of decomposition and is exceedingly 

 hard. 



All three specimens are from the Pennsylvanic (Lower Allegheny) 

 of Mazon Creek, Illinois. 



Trigonoscorpio n. gen. 

 This genus is characterized by the triangular shape of the cephalo- 

 thorax, comparatively thin and short tail the last segment of which 

 is 3-^/4 as long as wide, and by the hand with long fingers. The state 



