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Order Merocheta. 



Diplopoda with 19 or 20 segments, the superficial hardened parts of 

 which are coalesced into complete rings. Eyes are wanting in all 

 members of this order, which nevertheless contains a large proportion 

 of the bright-colored species of the Diplopoda. Nearly all Merocheta 

 have distinct lateral carinae or projections from the segments, on which 

 are located the repugnatorial pores or openings of glands which in 

 members of this order secrete prussic acid. 1 It is also characteristic 

 that the pores, which begin on segment 5, are not found on all the other 

 segments but are always absent, at least from segment 6, and usually 

 from several others. The normal or most general pore formula, that 

 which prevails on all the species described below, is 5, 7, 9, 10, 12, 



ANALYTICAL KEY TO WEST AMERICAN FAMILIES OF MEROCHETA. 



Body compact, the carinae overlapping or continuous ; claws of an- 

 terior legs of males abruptly curved beyond the middle. 



Family XYSTODESMID^E. 

 Body moniliform, the carinae distinctly separated; claws slightly and 



evenly curved. 



Repugnatorial pores lateral, located in small depressions of the 

 thickened margins of the carinae ; dorsal surface evenly convex, 

 smooth ......................................... Family CHELODESMID.-E. 



Repugnatorial pores dorsal ; margins of carinae not thickened ; 

 dorsal surface uneven with convex areas or granules. 



Family POLYDESMID^E. 



Family XYSTODESMIDJE. 



The family Xystodesmidaa, to which the genus Fontaria belongs, 

 is rich in species in eastern North America, but seems to have had no 

 corresponding prosperity on the Pacific Coast. Two species of Fon~ 

 taria have been described from California, but none is known from 

 Oregon or Washington, though there is no apparent reason why they 

 should not extend to British Columbia or southern Alaska, since the 

 eastern representatives of the family are found as far north as New 

 York and Michigan, where the climate would seem to be much more 

 unfavorable. 



The Xystodesmidae are recognizable among North American Mero- 

 cheta by their broad carinae, the margins of which appear nearly con- 



1 Science, N.S., xn, No. 301, pp. 516-521, October 5, 1900. 



