36 HISTORY OF CRUSTACEA. CHAP. V. 



pairs of feet, two other non-aquatic species of the same 

 family, which I have had the opportunity of examining, 

 agree with Ocypoda. One of these, perhaps Gelasimus 

 vocans, which lives in the mangrove swamps, and likes 

 to furnish the mouth of its burrow with a thick, cylin- 

 drical chimney of several inches in height, has the 

 brushes on the basal joints of the feet in question com- 

 posed of ordinary hairs. The other, a smaller Gelasimus, 

 not described in Milne-Edwards' ' Natural History of 

 Crustacea,' which prefers drier places and is not afraid 

 to run about on the burning sand under the vertical 

 rays of the noonday sun in December, but can also 

 endure being in water at least for several weeks, re- 

 sembles Ocypoda in having these brushes composed of 

 non-setiform, delicate hairs, indeed even more deli- 

 cate and more regularly constructed than in Ocypoda? 

 What may be the significance of these peculiar hairs, 

 whether they only keep foreign bodies from the 

 branchial cavity, whether they furnish moisture to 

 the air flowing past them, or whether, as their aspect, 

 especially in the small Gelasimus, reminds one of the 

 olfactory filaments of the Crabs, they may also perform 

 similar functions, are questions the due discussion of 

 which would lead us too far from our subject. Never- 

 theless it may be remarked that in both species, es- 

 pecially in Ocypoda, the olfactory filaments in their 



4 This smaller Gelasimus is also remarkable because the chameleon- 

 like change of colour exhibited by many Crabs occurs very strikingly in 

 it. The carapace of a male which I have now before me shone with a 

 dazzling white in its hinder parts five minutes since when I captured it, 

 at present it shows a dull gray tint at the same place. 



