MARINE ARTHROPODS 



291 



which, when fully grown, the front legs are much longer than in 

 the female. 



The remaining division of the crabs the Cyclometopa or Bound- 

 fronted Crabs, contains the larger number of species that may 

 truly be described as common objects of the shore, for while some 

 of them are well adapted for swimming, and live in the open water, 

 the majority inhabit the shore, either between or just beyond the 

 tide-marks, roaming about more or less freely when in the water, 

 but usually hiding under stones or weeds, or burrowing into the 

 sand, when left behind by the receding tide. 



FIG. 218. THE COMMON SHORE CRAB (Carcinus manas) 



The members of this tribe may be known at sight by the form of 

 the carapace, which is wide and rounded in front, and narrowed 

 behind. 



The accompanying illustration represents the commonest of 

 the group the Common Shore Crab (Carcinus mcenas), which is 

 found plentifully on all our coasts, and even in brackish water far 

 up the estuaries of rivers. It is a very voracious and pugnacious 

 creature, probably the most active of all our crabs, and its move- 

 ments, whether connected with its feeding, its sports, or its warfare, 

 are always very interesting when observed through clear water. 

 This crab varies considerably in colour, but is usually of the 

 greenish tinge shown in the frontispiece. 



