THE MTRIAPODA OF NORTH AMERICA. 



169 



Gen. 5. OPISTHEMEGA.* 



Segmenta podophora 21. Ocelli nulli. Labium plerumque dentatutn. Scutum postremum maximum, quad- 

 ratutn, alteris multo majore; pedes postremi crassi, breves. Appendices anales laterales obtusae. (Pigs. 8, 9, 10.) 



Feet-bearing segments 21. Eyes absent. Labium generally dentate. Last scutum very large, quadrate, much 

 larger than the others; last pair of feet thick, short. Lateral anal appendages obtuse. 



O. POSTICA. 



O. aurantiaca; capite polito, punctata; segmenta basali depressione triangulari mediana ; labio antice elon- 

 gate, mandibulisque punctatis ; laminis dentalibus subelongatis, margine Fin-. 8. Fig. 9. 

 antico fere recto; denticulis 6, distinctis, acutis; antennis haud pubescenti- 

 bus, 17 articulatis ; scutis sternisque politis ; scuto postremo subprofunde 

 punctata, postice abrupte truncate, medio canaliculate, lateribus rotundatis, 

 marginibus lateralibus valde elevatis; pedibus postremis brevissimis, subpro- 

 funde punctatis, subcylindricis ; articulis basali tibialique sine spin is, supra 

 subcomplanatis, intus complanatis, margine interiore superiore acute, alteris 

 rotundatis ; appendicibus analibus lateralibus angustis, dense profunde punc- 

 tatis, postice abrupte truncatis, sine spinis; squama preanali elongata, media 

 vix canaliculata. 



Orange ; head polished, punctate ; basal segment with a median triangular 

 depression; labium anteriorly elongate, together with the mandibles punc- 

 tate ; dental lamina somewhat elongate, anterior margin almost straight ; den- 

 ticules 6, distinct, acute; antennae not pubescent, 17 articulate; scuta and sterna polished; last scutum subpro- 

 foundly punctate, posteriorly abruptly truncate, medianly canaliculate, with the sides rounded, lateral margins 

 very elongate ; last pair of feet very short, subprofoundly punctate, subcylindrical ; basal and tibial joints 

 without spines, above subcomplanate, within complanate, superior interior margin acute, the others rounded; 

 lateral anal appendages narrow, densely profoundly punctate; posteriorly abruptly truncate, without spines; pre- 

 anal scale elongate, medianly scarcely canaliculate. 



O. postica, Wood, Journ. A. N. S., new series, 1863, vol. v, p. 35.. 



From the triangular depression on the basilar segment two sutures diverge posteriorly. 

 The scuto-episcutal sutures are very distinct, the sterno-episternal wanting. The sterna 

 are, however, provided with a mesial marking, the line of coalescence of the two primi- 

 tive sterna. The last pair of feet are rather shorter than in the following species, more 

 cylindrical and smoother, especially on their inner surface. The basal joint is rather 

 shorter than the tibial, which is about twice as long as the tarsal. Can this be the same 

 species as (Tryptojpa postica, Say? It agrees with Mr. Newport's description of his Theou- 



* Wood, Jourti. A. N. S., new series, 18G3, vol. v, p. 35. OkktSs, postice, jj-eya^. 

 vol. xrn. — 22 



