THE MYRIAPODA OF NORTH AMERICA. " 141 



18. POLYDESMIN.E. 



1872. — Polydesmia Humbert and Saussure. Miss, scientif. Mex. ZooL, VI, 25 (teste 



Latzel). 

 1880. — Cryptodesmoidea Karsck, Mittheil. Munch. Ent. Ver., 143. 



The subfamilies of Polydesmidce established by Humbert and Saus- 

 sure aud also retained by Latzel seem to me to be worthy of their rank. 



In accordance with common custom I have changed Polydesmia to 

 Polydesmince. 



19. SPHiEEIODESMEN T .E. 



1872. — Sphceriodesmia Humbert aud Saussure. Miss, scieutif. Mex. Zoiil., vi, 20 (teste 

 Latzel). 



20. Leptodesmus. 



1847. — Oxyurua Koch. Syst. Myr., 60 and 139 (vestitus). 



1859. — Leptodesmus Saussure. Linn. Ent., xm, 323 (granulosus). 



As Oxyurus Koch is preoccupied (Oxyurus Raf., Pisces, 1810; Oxyurus 

 Swains., Aves, 1827), Leptodesmus Saussure must be employed instead 

 of Oxyurus. 



21. Khacophorus. 



1847. — Rhacophorus Koch. Syst. Myr., 59 and 137 (Poly, conspersus Perty). 



1864. — Cryptodesmus Peters. Monatsber. kon. preuss. Akad. Wiss., 621 (alatus, etc.). 



Gryptodesmus has been rightly considered by Latzel as being a sub- 

 genus of Rhacophorus. 

 The following is a key to the subgenera: 



a. First dorsal plate normal, not concealing the head RHACOPHORUS. 



««. First dorsal plate strongly produced forward and completely concealing the head. 



Cryptodesmus. 

 22. Stenonia. 



1842. — Stenonia Gray. Todd's Cyclop. Anat. and Phys., in, 546 (druii). 



1847. — Platyrliqeux Koch. Syst. Myr., 59 and 131 (svaber = Stenonia, s. sir.). 



1860. — Odonlodesmus Saussure. Myr. Mex., 70 (javanus). 



1864. — Acanlhodesmus Peters. Monatsber. kon. preuss. Akad. Wiss., 547 (scutatus, etc.) 



Platyrhacus, Odontodesmus and Aeanthodesmus have been considered 

 as subgenera of Stenonia; but as Stenonia has not been properly sub- 

 divided — no subgenus Stenonia having been set apart — I have compiled 

 the following analytical key for the separation of the subgenera: 



a. Basal joint of legs not provided with a spine. 



b. Body slender, lateral carina- moderately developed, repuguatorial pores sub- 

 marginal, second dorsal plate much wider than the first Odontodesmus. 



bli. Body wide; lateral carina' strongly developed; repuguatorial pores superior, 

 more or less distant from lateral margin of canine ; second dorsal plate normal. 



Stenonia. 

 aa. Basal joint of legs armed with a spine Acanthodes.MUS. 



23. SCYTONOTLS. 



1847. — Scytonotus Koch. Syst. Myr.. 57 aud 130 (scabricoUis — granulatiis Say). 

 1864. — Trachelodesmus Peters. Monatsber. kon. preuss. Akad. Wiss., 623 (const) ictus). 



