The relationship between the palaearctic and nearctic faunas 283 



by Glick (1939, p- 29-30), as only small species, of the genera Bradycellus (Steno- 

 cellus), Micratopus, Microlestes (Blechrus), Tachystodes, and Tachys, were captured 

 at 5,000 feet or higher, one specimen of Microlestes pusio Lee. (less than 2 mm.) 

 at 10,000 feet. 



Vandel (1945) has drawn attention to the almost Amphiatlantic distribution of 

 the genera Porcellio and Metaponorthus and some other Terrestrial Isopods, and 

 regards this (p. 265-266) as a proof of Wegenerian connection. His maps show, 

 to my mind, that the world distribution of Wood-lice, notably in southern and 

 eastern Asia, is not yet sufficiently investigated to allow for conclusions of this 

 kind. 



Jeannel (1942, p. 115) regards the Palpigrad Arachnid genus Koenenia as a case 

 of direct transatlantic faunal exchange. Since one species is known also from Siam 

 (Kastner, 1932, p. 98), this argument has lost its force. 



The Cockroach (Blattodea) genus Arenivaga contains three subgenera, Arenivaga 

 s. str. being strictly American (southern U.S.A., Mexico), whereas subgg. Psammo- 

 blatta and Heterogamisca are chiefly Mediterranean (S Europe, N & E Africa, 

 Hither Asia). Bey-Bienko (1950, p. 300-323), who made a rearrangement of the 

 genus, regards its distribution (p. 302) as the result of a direct contact, in Wegener's 

 sense, across the present Atlantic, but the occurrence of species of Psammoblatta 

 as far east as Baluchistan, Afghanistan and West Turkestan makes this assumption 

 somewhat adventurous. 



The Oleacinidae, a family of terrestrial Gastropod Molluscs, is restricted to 

 America north to southern U.S.A., and the Mediterranean region (Pilsbry, 1946, 

 p. 188). However, it is a very old type, known in fossil state right back to Upper 

 Cretaceous of Europe, and it must be assumed that the family has undergone 

 great, still unknown changes of area during the course of the Tertiary. 



It is not surprising, with the above examples in mind, that several of the earlier 

 zoogeographers, especially, have tried to explain this type of disjunct distribution 

 by the assumption of some kind of land-connection also within the southern parts 

 of the North Atlantic, usually thought to have joined the Iberian Peninsula and 

 North Africa with the present West Indies {vide Scharff, 191 1, pp. 173, 214, 220, 

 271 a.f., fig.i4). Ihering (1927, pp. 26, 220) even boldly constructed one of "his" 

 bridges, the "Archatlantis", exclusively for the convenience of Sirenians of the 

 genus Trichechus, inhabitants of the sea, though as a rule, at least, of brackish 

 water (vide Holdhaus, 1927-28, p. 1051). In later years the supporters of land- 

 connections in this part of the Atlantic have usually been pronounced Wegenerians 

 who in cases of distributional pattern of the type exemplified above find biological 

 evidence in favour of the hypothesis of continental drift (vide next paragraph). 



Yet it seems to me that there is no need at all for a land-connection to explain 



