CRAB GENERA PLANES AND PACHYGRAPSUS — CHACE 

 Table 2. — Mean values of carapace proportions 



73 



Table 3. — Mean values of total length of three distal segments of second walking leg 



shorter legs may be better adapted to this more sessile existence or, 

 conversely, the longer legs of the smaller individuals may be advan- 

 tageous in scurrying and swimming about among the floating weed. 

 Whether there is a gradual reduction m the relative lengths of the legs 

 with the transfer of the animal to a different means of transport or 

 whether there are two forms of Planes in the North Atlantic — a small, 

 trapezoidal form that spends its entire life on floating weed and a 

 larger, laterally convex, and short-legged form that lives only on 

 flotsam and turtles — can be determined only when more material, 



874803—51 2 



