RACERS 85 
armed. M. Jobert, in examining the breathing apparatus 
_of land-crabs, has found that of Uca una to be the most 
complete. ‘There is a regular movement of inspiration 
and exspiration to keep the air from stagnating in the 
breathing chamber, and between the third and fourth and 
the fourth and fifth limbs there are small supplemental 
inspiratory orifices coated externally with long hairs (see 
Sp. Bate, ‘ Brit. Assoc. Report,’ 1880). 
Family 2.—Ocypodide. 
The carapace is in general moderately convex, cancroid 
or trapezoidal, with the antero-lateral margins straight or 
arcuate, the branchial regions not greatly dilated. The 
‘front’ is of moderate width or very narrow. The orbits 
and eye-stalks are of moderate size or greatly developed. 
The third maxillipeds have the fifth joint articulated at 
the front inner or rarely at the front outer angle. The 
chelipeds in the adult males are in general of moderate 
size, sometimes slender and elongate. The seventh joint 
in the walking legs is stiliform, without strong spines. 
The pleon does not always cover the whole width of the 
sternum between the last pair of legs. 
The species are generally small, littoral, or inhabitants 
of shallow water, but are not unknown from considerable 
depths. There are nearly forty genera assigned to the 
various subdivisions of this family. 
Ocypodé, Fabricius, 1798, has the orbits very large 
and open, extending all along the anterior margin on either 
side of the narrow and deflexed ‘front.’ The eye-stalks 
are large, with a short basal joint, the terminal part often 
prolonged distally as a spine or tubercle, the large cornee 
covering much of the lower surface of this terminal joint. 
The chelipeds in the adult male are unequal and well de- 
veloped, and usually the palm has a vertical series of short 
raised lines or tubercles on the inner surface, which form 
a stridulating ridge. 
As the name swift-of-foot implies, these Crustacea are 
especially noted for their rapidity of movement. They are 
just the opposite of some of the strong-armed, thick- 
