130 



Alexander Petrunkevitch, 



Found in the Pennsylvanic (Lower Allegheny) of Mazon Creek, 

 Illinois. 



Architarbus horribilis (Mclander). 

 Plate XII, fig. 71; text figs. 83, 84. 

 = Hadrachne horribilis Melander, Jour. Geol., Vol. XI, 1903, 

 p. iSo, pi. V, fig. I ; pi. VII, fig. i. 



The type and only specimen of this species, No. 9232 of the 

 \\'alker Museum of the University of Chicago, presents only the 



Fig. 83. Fig. 84. 



Figure 83.— Architarbus horribilis (Melander), holotype, Univ. of Chicago 

 Mus. Xo. 9232, dorsal surlace showing cephalothorax and abdomen. 

 Figure 84. — Same, showing the ventral surface. Both surfaces appear in 

 the specimen superimposed, and since the reverse is missing the sternites 

 are not visible. X -^ 



obverse with the ventral surface superimposed on the dorsal. Partly 

 owing to this, partly to the fact that the specimen was not suffi- 

 ciently cleaned, the description of Melander is incorrect in several 

 respects. Moreover, he committed the same error as Scudder in 

 two instances, by assuming the legs of the first pair to be the 

 pedipalpi. 



Total length 38.0 mm. Cephalothorax 18.3 mm. long in middle 

 line, 16.3 mm. wide at posterior corners which are not rounded. 



