WOOD-LICE AND SPIDEES 191 



where this spider occurs. The silk spider is known from 

 Brazil, from Central America as far north as Texas, and from 

 Southern Florida. Professor Dahl * argues that the group to 

 which this species belongs already had a wide range in Cre- 

 taceous times. Its nearest relation, Nephila clavata, is pecu- 

 liar to China and Japan. It is quite possible, therefore, that 

 the American form may have existed since early Tertiary 

 times. But, as 'Dr. Marx f observes, the spiders introduced by 

 human agency have not only acclimatised themselves ; they 

 have also, in a more or less marked degree, driven away and 

 exterminated the indigenous spider fauna. Yet among the 

 remnants of that ancient fauna we recognise four species that 

 are peculiar to Bermuda. Most of the remainder are identical 

 with American forms. 



One of the most noteworthy animals that might be adduced 

 in favour of the theory that Bermuda represents the remnant 

 of a large land surface once connected with the mainland is 

 the land nemertean Geonemertes agricola. This very pecu- 

 liar worm is found in abundance at several distinct localities 

 in Bermuda. It might be said that this worm is not of much 

 zoogeographical value, since it is able to resist immersion in 

 sea-water for some time. On the other hand, it must be re- 

 membered that land nemerteans have an extremely discon- 

 tinuous range on ancient land surfaces. Hence their distribu- 

 tion is suggestive of great antiquity. Nine species of the 

 genus Geonemertes are now known from Australia, New Zea- 

 land, New Guinea, Pelew Islands, Rodriguez Island, the 

 Seychelles and Bermuda. To suggest that Geonemertes 

 agricola owes its presence in Bermuda to an accidental intro- 

 duction would be quite inadmissible, because it has neves 

 been found elsewhere.J 



Of greater importance than any of the foregoing inverte- 

 brates are the land and fresh-water snails inhabiting 

 Bermuda. Dr. Pilsbry distinguishes autochthonous species, 

 drift waifs from the West Indies, and snails imported by the 

 agency of man. The last group we need not consider here, 



* Dahl, P., " Verbreitung d. Spinnen," p. 278. 

 t Marx, a, " Spiders of Bermuda," p. 100. 

 I Ooe, W. E., " Geonemertes agricola," p. 634, 



