234 HALF AN HOUR WITH CRUSTACEA. 



plates forming it do not quite meet, and that the 

 edges are not fastened. The legs are articulated to 

 the under side, and as the gills, or branchiae, are 

 placed within this large plate, beneath, and air can 

 only be supplied by fresh sea-water, it follows that 

 every time the legs are moving about, in swimming 

 or otherwise, they are pumping fresh air to the 

 gills, as well as serving for locomotive purposes. 



Commencing with the crabs, it is to be observed 

 that these animals are not met with in high lati- 

 tudes. They are most abundant in seas that are 

 warmer than our own, abounding in tropical regions, 

 and attaining their northern boundary in our own 

 seas, where they are far from uncommon, either in 

 species or individuals. Among these, the group 

 called " Spider-crabs," on account of their long, 

 spider-like legs, are perhaps the most abundant, and 

 may be found lurking under stones, &c., at low 

 water. One of these, commonly called the " Cor- 

 wich " (Maia squinado), Fig. 126, lives in deeper 

 water, and is a great trouble to the fishermen, as it 

 enters the crab and lobster pots and eats up the bait, 

 and by its restless moving about frightens away the 

 Crustacea which the fisherman is endeavouring to 

 entrap. In this species the carapace is ovoid and 

 set all over with spines, whence its name. A great 

 difference in appearance, however, results from the 

 difference in age of the individuals. It is a very 

 common species, and sometimes is as much as eight 

 inches in length. In many places it is eaten by the 



