788 R. I. pococK 



the Burmese fauna. Moreover the known l^urmese genera are 

 readily divisible into three sections ; the first is represented by 

 the single genus Platyrrhachus, the second by the genera allied 

 apparently to the aiiil)iguous genus Cryptodesmus and the third, 

 which is much the richest faunistically, by the genera related 

 to Strongylosoma. 



The genera of the second category have already been sepa- 

 rated out of the old family Polydesmidae by Dr. Karsch as a 

 special subfamily Cryptodesmidae , and the group has recently 

 received the rank of a family at the hands of Sig. Filippo Sil- 

 vestri (^). This leaves the other two groups to be accounted 

 for. But pending a much needed revision of all the known ge- 

 nera of Polydesmoidea, I propose to regard them as two families 

 under the names Plalyrrhachidae and Polydesmidae. 



The three may be briefly tabulated as follows : 



A. The tail very wide, squared or semicircular; pores 



situated on the upper side of the keels and lying in 

 the centre of a perfectly smooth circular disc, the 

 disc with its central aperture exactly resembling the 

 muzzle of a cannon Platyrrhachidae 



B. Tail wider at the base than at the apex, subcylindrical 



or triangular, the apex bluntly rounded or truncate 

 and bifid; pores (in Burmese genera) situated on the 

 margins of the keels, the area around them swollen. 

 Keels large or small, horizontal or elevated, when 

 large not depressed but raised Polydesmidae. 



C. Tail triangular, pointed; keels large and depressed, 



completely concealing the legs. Pores when present on 



the upper side of the keel Cryptodesmldae. 



Family PLATYRRHACHIDAE nov. 

 1. flatyrvliaelius andersonii, sp. n. 



Syn. Acanthodesrnus pilipes, Peters; Pocock, Journ. Linn. Soc. Zool. XXI, p. 291. 



Recorded originally from Morgui, where it was obtained by 

 Dr. J. Anderson. Sig. Fea brought back specimens from Malewoon 



(') Ann. Mas. Civ. Genova (2) XIV, 1895, p. 647. 



