1520 



CRUSTACEA. 



Before stating the conclusions from the above tables of the Tetra- 

 decapoda, it should be observed that this division of Crustacea has 

 been less thoroughly explored than that of the Podophthalmia, and 

 future investigations inust vary much the proportions between the 

 species of the different regions. The coasts of Europe and the 

 northern seas, are within the reach of European zoologists, and have 

 been carefully examined; while voyagers through the tropics have 



