668 PEOCEEDINGS OF THE NATIONAL MCSEVM. 



Segments 1-5 with a single ])air of legs each; plursB indicated by a longitudinal 

 suture, which is ni<t above by two transverse siuures crossing tlie dorsal part of the 

 segment; labrnni with a median sintis: Order Axociieta. 



Segments 3 or 1 footless, segment ;") with two pairs of legs; plnrje entirely obliter- 

 ated; transverse suture single or wanting; labrum witli a median tootli 



Gnathochilaiium with stipes broad at base, in contact in tlie median line between 

 the nientum and promentum; external seminal ducts adnate : Order Zygocheta. 



Gnatliocliilarium witli stipes narrower at base, widely separated l)y th« mentnm 

 and promentum, which ai-e in contact; external seminal ducts distinct or want- 

 ing 



Pedit^erous lamina- Iree througiiout; external seminal ;liiet8 wanting, tins aper- 

 tures being located in the coxa; of the second pair of legs: Order CVklociieta. 

 Pedigerons lamina- adnate (except the first two) ; external ducts distinct: Ordei' 



DlPI,0< IIKTA. 



Order CCELOCHETA Cook. 



Vwlocheia Cook, American Naturalist, Di-cember, 1805, p. 1115; Brandtia, 

 1896, p. 8. 



Labruni tiidentate, with a median tootli. 



Mandibulary stipe with a distinct cardo, not areate. 



(riiathochilarinin with stipes proximally separated by the mentum; 

 cni'do small. 



Mentum large, entire, traj)ezoidal or semielliptic. 



Promentum small, triangular, included between the bases of the 

 lingnal lamina' (obsolete in some Chordeumat(udea). 



Lingual lamina' distinct; lingual lobes })rovided with sense cones. 



Mediau lobe well developed, with a stylifbrm or tridentate chitinous 

 ])roce8s on each side. 



Last segment at apex with a i)air of articulated setiferous papilhe 

 known in some cases to function as si)inning-organs. 



Pedigerons lamina' all free; pleurae compk'tely coalesced with scuta. 



Legs seven-Jointed (excei)t the tirst two pairs, which are six-jointed), 

 second Joint very short. 



Genital oi)enings of males in the posterior face of the coxa' of tlie 

 second pair of legs 



Legs of tiie seventh segment, and usually some others, modified for 

 copula tory ])urposes. 



Tlie members of this order are distributed throughout tlie north tem- 

 l)erate /.one, with outliers known from the mountains of the Malay region 

 and from New Zealand. 



The attinities of this order are probably with the iMerocheta, but it 

 must be admitted that the characters on which this inference is based 

 are mostly primitive rather than derivative, and are shared also by the 

 Mouocheta. The great external similarity of the orders of the I'hilo- 

 gratha is explainable by the fact that they have not differentiated in 

 response to habits changed by entering different fields in the e(;onomy 

 of nature. Their wonderfully fixed structural differences can not on this 



