The barnacles are only able to attach them selfs to surfaces in the water. Since the surface is limited, barnacles are attaching themselves to the other barnacles, crowding the rock. The muscles were not able to grow or attach themselves off the surface of the rock. Same thing with the mussels that are growing on the rock. So not only barnacles are crowding the rock, but Mussels as well are crowding the rock.
 
        
             
        
        
        
Answer:
It should be the reptile at the top right of the picture 
Explanation:
Some reptiles do not go over India (including the two at the bottom)
 
        
             
        
        
        
Amount of wear, and how long they are may contribute with age and maybe even coloration and pigment.