HERMIT-CRABS. 333 



pincers, chooses large shells within which it can retire well out of 

 reach when alarmed. The Coenohita, with its stout pincers, prefers 

 shells much smaller, relatively speaking, and ensconces itself snugly 

 in the body whorl, forming an operculum with its claws. As the 

 hermit-crab, Coenohita, crawls along the dry sand of a beach, it 

 leaves behind it characteristic pinnate tracks which may be often 

 traced for several feet. The lateral markings are produced by the 

 claws and le£;s workinor on each side of the shell; whilst acentral groove 

 is formed by the weight of the shell itself As shown by the arrow in 

 the diagram, the lateral markings point in the direction of the course 

 which the hermit-crab has taken. Sometimes only a single row of 

 lateral tracks accompanies the grooves produced by the shell. Such 



markings were produced by a 

 hermit-ci'ab when frightened by 

 my approach. It turne dits front 

 towards me, and crawled back- 

 wards, by working most of his 

 claws and legs on one side of the 

 shell. In the case of the larojer hermit-crabs, which are much less 

 frequent on the beach, each limb produces a distinct print on the 

 sand ; but with the small species of Coenobita which infests the 

 oeach, each lateral marking, as shown in the diagram, is produced 

 by a single movement of the claws situated on the same side of the 

 shell. The hermit-crabs only leave their tracks on the dry loose 

 sand. One individual, that I placed on sand, still wet from the re- 

 treating tide, crawled along v/ithout leaving any impression. I have 

 described these impressions with some care, as they bear on the 

 origin of the surface-markings of rocks of shallow-water formation, 

 a subject recently discussed in the geological world. It is highly 

 probable that some of the larger and heavier forms of the Anomura 

 (and, in fact, of the Decapoda generally) would produce prints 

 such as I have here described, both on mud-flats left dry by the 

 tide, and on the soft bottom in shallow depths. A cast of the 

 impressions thus produced would have an unmistakeable plant-like 

 form. 



Whilst examining the island of Simbo, I noticed some singular 

 Medusoe in a small mangrove-swamp, which is inclosed in the low 

 point that forms the south shore of the anchorage. Numbers of 

 these organisms of a large size (8 or 9 inches across the umbrella), 

 and of a dirty-white colour, were lying on the mud with their 



