PELAGIC FLOATING CRUSTACEA 155 



There are a few Crustacea living habitually on the 

 high seas which cannot be reckoned as belonging 

 either to the true plankton or to the necton, since 

 they depend on outside help for keeping themselves 

 afloat. Among these are the Barnacles which cluster 

 on logs of drift-wood, and are among the most 

 important causes of the " fouling " of ships' hulls on 

 long voyages. The stalked Barnacles of the genus 

 Lepas are especially common in such situations, and 

 the characters of their larvae have been already 

 alluded to. Certain species of sessile Barnacles are 

 constantly found attached to large marine animals. 

 For example, Chelonobia adheres to the shell ot 

 Turtles, while Coronula and some allied genera are 

 found on Whales. 



The little " Gulf-weed Crab " (Planes minutus 

 Plate XIX.) is found clinging to floating drift-weed 

 nearly everywhere throughout the temperate and 

 tropical seas of the globe, and is especially common 

 in the area known as the Sargasso Sea, in mid- 

 Atlantic. It is occasionally drifted to the south 

 coasts of the British Islands. In Sloane's " Natural 

 History of Jamaica," published in 1707-1725, it is 

 stated of the Gulf- weed Crab that " Columbus, find- 

 ing this alive on the Sargasso floating in the sea, 

 conceived himself not far from some land, on the 

 first voyage he made on the discovery of the West 

 Indies." 



A few other Crustacea also form part of the 



