DIPLOPODA. 13 
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Class DIPLOPODA (Millipedes). 
The dominant Central American forms of the Calobognatha or suctorial millipedes 
belong to the genus Platydesmus of the family Platydesmide. This family also has 
representatives in North America, Amurland, Malaysia, and the Mediterranean area 
in Europe. It has not been recorded as yet from tropical Africa, India, or Australia. 
Hence the known facts of its distribution point to its evolution in the Northern 
Hemisphere and to its failure to penetrate into the ancient southern continents. 
If the Mediterranean species referred to Platydesmus belong, as is probable, to a 
distinct genus, Platydesmus is restricted to Central America (Mexico, Guatemala). 
The Chordeumoidea are divisible into two families—the Heterochordeumide, 
ranging from India to New Zealand, and the Chordeumide, which are abundant in 
North America and Europe. Their range eastward from Europe into Asia has not 
been ascertained, but there seems no doubt that they are absent from tropical Africa. 
The described Central American species, from Mexico and Guatemala, belong to a 
genus (Cleidogona) also existing in North America. No species have been discovered 
in South America or in the Antilles. This element, therefore, of the Diplopod fauna 
of Central America was no doubt derived from North America. 
The Stemmiuloidea are an obscure group, known at present only from tropical Asia 
(Ceylon), tropical Africa (Liberia), and tropical America (Colombia, Panama, and 
Porto Rico). Probably these Diplopods await discovery elsewhere ; but, so far as is at 
present known, they may be described as southern. Perhaps the most interesting 
point connected with their distribution is the ascription to the same genus (Dopsiuius) 
of the Ceylonese, Liberian, and Porto Rican species. ‘This classification accords 
with the theory of the former existence of a tropical] transatlantic connection between 
the Greater Antilles and West Africa. 
The Central American forms of Iuloidea, Paraiulus, from Mexico and Guatemala, 
are closely akin to genera and species now living in North America. The nearest ally 
of Paraiulus in the Old World is Mongoliulus, recorded from Corea. Here again 
there is evidence for a northern derivation of this element of the Central-American 
fauna. : 
As an explanation of the occurrence of the suborder in North America and Europe, 
it may be suggested that it formerly extended across the Northern Atlantic when 
temperate conditions prevailed in Greenland, Iceland, and the now-vanished land-areas 
which are believed to have joined these countries and Europe and America in one 
continuous tract. 
Of the Spirostreptoidea, the single Central American genus of Spirostreptide 
(Orthoporus) is mainly South American in distribution ; but it is closely allied to, if 
not identical with, millipedes of the same family now found in tropical Africa, but not 
