HISTORICAL ZOOGEOGRAPHY 109 



The camel family is now represented in Asia by true camels, and in 

 South America by the llamas and their relatives. This group had 

 representatives in North America from the Eocene to the Pleistocene, 

 and this affords a satisfactory explanation of the present discontinuity. 

 The pleurodiran turtles are now confined to the southern hemisphere, 

 where they are widely distributed, but fossils of this type are known in 

 Europe from the Upper Triassic to the Miocene, in Egypt from the 

 Eocene to Mid-Pliocene, in India in the Lower Eocene, in New Zea- 

 land and North America in the Upper Cretaceous, and in the South 

 American Eocene. 29 Direct connections between the southern continents 

 are accordingly not required to explain the present distribution of the 

 side-necked turtles. Whenever good palaeontological evidence is avail- 

 able, and when the relations have been adequately studied, a similar 

 explanation seems to apply to the widely distributed families and 

 genera of fishes, amphibians, and reptiles, whose present distribution 

 is often a mere relict of a former world-wide range. 



Although fossil remains of insects and spiders are relatively scarce, 

 these groups also afford instructive examples of a more extensive dis- 

 tribution in the past, with a discontinuous or restricted distribution at 

 the present time. The genus of ants, Oecophylla, now has a species in 

 Africa, one in the East Indies, and a third in Australia and in the Aru 

 Islands; but no less than four species are known from the European 

 Tertiaries, and the genus was doubtless widely distributed in Eurasia. 30 

 Another ant genus, Ectatomma, with numerous species in the tropics 

 of America, Asia, and Australia, is represented by a species in the 

 Oligocene Baltic amber and by another in the Miocene Sicilian amber. 

 A third genus, Macromischa, has now two species in West Africa and 

 eight in Cuba and Mexico; five species are known from the European 

 amber. 30 The related lucanid genera, Lamprina and Neolamprina in 

 South America and Sphenognathus in Australia, are connected by an 

 intermediate form Palaeognathus succini in the Baltic amber. 



Termites, represented in the tropics and subtropics by more than 

 1600 species, are now scarce in the temperate zones, a single species 

 reaching southern Europe, though several reach the same latitude in 

 North America. About fifty species of termites are known from the 

 North American and European Tertiaries. 30 The primitive family of 

 spiders, Archaeidae, survives with three genera, one in Patagonia, one 

 in the Congo, and one in Madagascar; it is represented by six species 

 in the European amber. 31 There are numerous other examples of this 

 nature, and their number is likely to be greatly increased with the 

 progress of palaeontological research. Although the incompleteness of 

 the palaeontological record prevents the general application of this 



