EACEES 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. — Ocypodidai. 



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. 



Ocypode, 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 cornesB 

 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- 



