4 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.72 



but not known previously in the United States The location might 

 appear most unlikely for the survival of a tropical type — an elevated, 

 exposed place where in cold periods the ground probably freezes to 

 a depth of several inches. The vegetation is sparse, with scattered 

 small junipers, shrubby oaks, and bushes. Probably the most essen- 

 tial feature of the environment is the very coarse, open soil formed 

 of decomposing granite. The creatures were found under stones with 

 clean surfaces underneath. In no case were millipeds found under 

 stones where the surfaces were coated with dark colloidal material, 

 which also discolors the gravel and doubtless represents a different 

 condition of the soil. The place was in a divide a few miles from 

 Miami, in the direction of Superior. 



Though surrounded by very broken country, the spot was nearly 

 level and with no through drainage or flooding of the surface. It 

 seems that the humus faunas of colloidal regions are limited to spots 

 where a humus blanket has accumulated above the soil, or where the 

 surface is not flooded even in heavy rains. Thus the restriction of 

 the new tropical milliped to the very small area in which it was found 

 could be considered as a special and rather striking illustration of a 

 general relation that had beeii observed in the study of the humus 

 fauna. 



From the distribution of the humus fauna it may be possible to 

 throw light on the question of the natural conditions in the south- 

 western area before the period of human activity, or even further 

 back. There can be little doubt that the surface conditions have 

 been greatly changed during the human period, and the archeologicai 

 indications of extensive and long-standing human occupation in 

 this region are accumulating. Whatever the causes of the changed 

 conditions, wider and more continuous distribution of the humus 

 fauna in former times is hardly to be doubted. 



CHARACTERS OF THE COLOBOGNATHA 



The Colobognatha, as the name indicates, are millipeds with a 

 restricted development of the mouth parts and other cephalic 

 organs, except that the antennae are relatively large. The mouth 

 parts especially are reduced or much less developed than in the 

 other orders, and have been described as suctorial rather than man- 

 ducatory, after the analogy of insects. The labral region of the 

 head in most of the genera is narrow or is produced into a sharp 

 beak. A remarkably divergent genus described in this paper has 

 the head broadened below instead of narrowed. 



The structure of the segments is primitive rather than specialized, 

 with as wide a diversity of form as in any other order of millipeds. 

 The segments of most of the genera are definitely flattened, in con- 



