ScHAiiFF — ^S'o;;^^ liciJiarh on the Atlantic Problem. 29-3 



doubt, are iutroduccd by mau Avitli pluuts and iu packiug-cascs. 

 They not only form the exception among Avoodlice, but they rarely 

 spread far beyond human habitations, and are easily recognisable as 

 intruders. 



From th^ researches of Dollfus and ^^orman, Avhu have given us 

 valuable reports on the -woodlice of the Azores and Madeira, we notice 

 that they are mostly identical with those of Europe and North Africa, 

 and that there is likewise an endemic element. Some characters in 

 the fauna of these islands seem to support the view that they have 

 not long ago formed part of the continent of Europe. Philoxia 

 Couchi — a species which occurs on the shores of the Mediterranean 

 under sea-weed, and extends along the Atlantic coasts of Europe as 

 far north as the south of England — also inhabits the Azores and the 

 Canaries. Among the rocky coasts of the Atlantic, we lind another 

 species, much more common than the last — viz., Ligia oceanica, which 

 is replaced in the Mediterranean by L. italica ; but the latter form 

 turns up again on the coasts of the Canary Islands, the Azores, and 

 Madeira. 



In the Canary Islands, a species of the peculiar blind woodlouse, 

 Flatyarthrus, has been discovered, which inhabits the subterraneau 

 burrows of ants. One cannot conceive of any accidental means of 

 transport to an island of such a creature, and the occurrence of 

 Flatyarthrus Schohli — a Mediterranean form — iu Teneriffe is a very 

 convincing argument in favour of aland-conneetion with North Africa 

 in late Tertiary times. Nineteen species of terrestrial Isopods are 

 known from the Canary Islands, sixteen from the Azores, and twelve 

 from Madeira. 



There is little in the crustacean fauna of either Madeira or the Azores 

 wliich might lead us to believe that they were once connected by land 

 with America; but it is different with the Canary Islands, which 

 probably formed part of a laud stretching, as was suggested before, 

 from North Africa to South America. 



The genus Flatyarthrus, including several small blind subterranean 

 species, is represented by three species in Western Europe and North 

 Africa, one of whick, as we have seen, reached the Canary Islands. 

 The only other species of the genus F. Simoni has been discovered in 

 Yenezuela, in South America. 



Take again, Porcellio, an almost essentially European and North 

 African genus. "VVe find one species peculiar to Yenezuela. Metopo- 

 northus, evidently an ancient genus, is also mostly European : but 

 one species has spread eastward to Sumatra, another is found in North 



