HABITS OF CRUSTACEANS. 401 



the cylindric holes of Gelasimi, Ocypode, and Gonoplax. 

 When their communities are no longer flooded by the 

 water, these bustling little Crustaceans make their ap- 

 pearance in dense crowds, but retreat on the slightest 

 alarm to their subterranean burrows. They are of every 

 variety of colour, some of them being milk-white, some 

 purple, others reddish, and many perfectly black. So 

 numerous are these Crabs, that seen at a little distance, 

 they give the soil a variegated aspect, nearly obscuring 

 the original blue colour of the mud. A Crab, with a trian- 

 gular carapace, of a light brown, is also common among 

 the tufts of grass in the vicinity. 



A. few remarks on the habits of certain genera of Crus- 

 taceans, which I have noticed in the course of our wan- 

 derings, may be deemed of interest by some of my 

 readers, although the subject will be more fully treated 

 of in another work. The Grapsi are more varied in their 

 habits than is generally supposed. The common species 

 (G. varius] and others, are found running over the rocks 

 near the sea, feeding on the Periopthalmi, Blennies, 

 and other fish, that quit the water for short inter- 

 vals, and attacking occasionally the sessile Cirrhipeds, 

 as Balanus and Conia, fixed on the surface, or that 

 pedunculated one which fills up the fissures, the Poli- 

 cipes. Darwin tells us, he has seen them come to the 

 nests of Sea-birds, and without ceremony help them- 

 selves to the fish which the parent birds had brought to 

 feed their nestlings. They run with the greatest rapidity, 

 and are very cunning and difficult to capture. There is 

 one species, however, (G.latifrons, White) that I have found 

 inhabiting fresh-water rivulets and ponds, which has all 



VOL. II. 2 I) 



