CRABS, ETC. 



FIG. 99. Marine cray-fish (Pahnurus vu/garis), about i natural size. 



NOTE. On the Florida reef nearly every coral head or branch 

 affords protection to one or more cray-fishes, as they are there called. 

 The animals partly undermine them, thus serving the coral by pre- 

 venting the fatal inroads of sand and mud. 



