seven o’clock
In the midst of this moving vegetation , under arbors of water plants , there raced legions of clumsy articulates , in particular some fanged frog crabs whose carapaces form a slightly rounded triangle , robber crabs exclusive to these waterways , and horrible parthenope crabs whose appearance was repulsive to the eye . One animal no less hideous , which I encountered several times , was the enormous crab that Mr. Darwin observed , to which nature has given the instinct and requisite strength to eat coconuts ; it scrambles up trees on the beach and sends the coconuts tumbling ; they fracture in their fall and are opened by its powerful pincers . Here , under these clear waves , this crab raced around with matchless agility , while green turtles from the species frequenting the Malabar coast moved sluggishly among the crumbling rocks . Near seven o'clock we finally surveyed the bank of shellfish , where pearl oysters reproduce by the millions . These valuable mollusks stick to rocks , where they 're strongly attached by a mass of brown filaments that forbids their moving about . In this respect oysters are inferior even to mussels , to whom nature has not denied all talent for locomotion . The shellfish Meleagrina , that womb for pearls whose valves are nearly equal in size , has the shape of a round shell with thick walls and a very rough exterior .