THE CRUSTACEA 165 



It is named Pirimela denticulata. It measures about half- 

 an-inch across the back, and the sides and front of its 

 carapace are armed with strong and sharp denticulations 

 (hence its specific name). Its colour is olive-green, with 



Fig. 71. Corystes cas-nvelaunus. Male, f Natural size 



red and white markings. It is considered very rare, but 

 this is owing to its habits ; for, as a matter of fact, it is fairly 

 numerous. It buries itself just below the surface of shell 

 gravel, where there is such in crevices at the foot of rocks 

 at the lowest tide zone, and here, of course, readily escapes 

 detection, except by the experienced shore hunter. 



