234 synopsis of north american myriapoda. 



Gen. Opisthemega. 



Opisthemega. Feet-bearing segments 21. Eyes none. Last scutum the largest. 



0. postica. Basal joint of last pair of feet not armed with a spine, and its margins not 

 serrulate. 



0. spinicauda. Basal joint of last pair of feet armed with a spine, and its inner mar- 

 gins serrulate. 



Gen. Theatops. 



"Eves distinct. Feet-bearing segments 21. Joints of the last pair of feet obconic, 

 large, abbreviate." 



T. postica.^ 



(ten. Scolopocryptops. 



Eyes none. Feet-bearing segments 23. 



Margin of the labium nearly straight. 



S. sexspinosa. Scuta not rugose. Lateral anal appendages with a very minute rudi- 

 mentary spinule on their supero-posterior angle. 



S. spinicauda. Scuta somewhat rugose. Lateral anal appendages with a well-pro- 

 nounced, black spinule on their supero-posterior angle. 



Margin of the labium shaped like an inverted w. 



S. gracilis. Basal joint of last pair of feet longer than the tibial ; the three last joints 

 only pubescent. Lateral anal appendages elongate. 



S. lanatipes. Basal and tibial joints of last pair of feet about equal. Tibial, tarsal, 

 and metatarsal joints roughly pubescent. Lateral anal appendages short. 



fam. geophilid^;.. 



Anterior subsegment of each segment not completely atrophied. Segments very nume- 

 rous. Antenna? 14 articulate. 



Gen. Mecistocephalus. 



Cephalic segment elongate, narrow, more than twice longer than broad. Prebasal seg- 

 ment separate. Basal and subbasal segments coalescent. 



M. f ulcus. Fulvous. Head light orange. Cephalic segment rapidly contracted and 

 rounded oft" at its posterior end. Pairs of feet 57. 



M. limatus. Orange] Head deep red. Cephalic segment regularly narrowed from 

 the front. Pairs of feet 43 — 4 I. 



