276 MARINE INVERTEBRATES 
erabs of this species are very active and can swim rapidly. They also 
have the habit of pushing themselves backward into the mud for con- 
cealment. They are predaceous and pugnacious, and have great strength 
in their claws, which they use with dexterity. They not only fight their 
own kind, but show a bold front to all enemies, including man. The 
average size is six inches across the carapace. 
Genus Ovalipes 
O. ocellatus (Rathbun), Platyonichus ocellatus  (Latreille), 
the lady-crab or sand-crab. A species common on sandy shores from _ 
Cape Cod to Florida. It is found among the loose sands at low-water 
mark, even on the most exposed beaches, ard also is abundant on sandy 
bottoms offshore. At low-water mark it buries itself up to the eyes 
and antenn® in the sand, where it watches for prey and foes, and quickly 
WIAA, 
Ovalipes ocellatus, the lady-crab. 
disappears beneath the sand when danger approaches. It possesses the 
power of burrowing in common with other marine animals which inhabit 
exposed beaches of loose sand. By burying: itself deep in the sand it is 
protected from the action of the breakers. This species is easily dis- 
tinguished by the color and shape of its carapace, taken in connection 
with its posterior swimming-feet. The body is nearly as long as it is 
broad, with five prominent spines on each side. The front margin is 
indented on each side of a three-spined rostrum, to form cavities for the 
eyes. The first limbs are large and have claws; the posterior ones are 
flattened into swimming-feet, and the intermediate three pairs are sim- 
ple in structure, ending in points. In color it is white, covered with 
spotted rings of red and purple. 
