48 



Alexander Petriinkevitch, 



Palaeopisthacanthus n. gen. 

 Sternum pentagonal. Hand with long fingers. Post-abdomen 

 very short and slender. Genotype P. schucherti n. sp. 

 Key to the Species of Palaeopisthacanthus. 

 Cephalothorax widest a little in front of posterior edge, and here 

 wider than long. 



P. schucherti n. sp. 

 + cephalothorax widest at posterior edge, slightly longer than wide 



P. mazonensis n. sp. 



Palaeopisthacanthus schucherti n. sp. 

 Plate II, figs. 8, 9; text figs. 11, 12. 

 The type specimen, the only one of the species in existence, is 

 in the collection of the Peabody Museum under the number 140. 



Figure ii. — Palaeopisthacanthus schucheyti n.^sp., holotype, Peabody Mu? 

 No. 140, ventral surface. Figure 12. — Same, j dorsal surface. X y 



It is an excellently preserved specimen, showing both the obverse 

 and reverse with great detail. The obverse shows both mandibles 

 and palpi, the cephalothorax with the median eyes, the abdomen, the 

 fifth post-abdominal segment with poison gland and fragments of legs 

 to the left of the body ; the reverse, both mandibles, one pedipalp, 

 sternum with coxae, genital opercula, abdomen and fragments of legs. 

 Total length about 16 mm. Cephalothorax 3 25 mm long, 4.25 

 mm. wide in the widest place, and 3.75 mm. wide at posterior edge, 



