TO INDIAN CAECINOLOGY. 331 



flat expanse of sand or mud, which frequently extends seawards Cor some considerable 

 distance. In the tidal belt blocks of dead and water-worn coral are strewed about, and 

 in places these enclose artificial rock pools, in which Crustacea, Molluscs, Sponges, 

 Holothurians, &e. are very abundant. The Crustacea most commonly met with at low 

 water are : — Atergatis floridus, Leptodius exaratm, Pilumnus oespertilio, Eriphia Icevi- 

 mana, Thalamita prymna, 3Ietoporjrapsiis messor, Leioloplms planissimus, PetroUsthes 

 deniatus, and Oonodactijlus (jlaher. Of these it may be mentioned that the Pilumnus is 

 remarkably sluggish and apathetic ; the Thalamita is extremely active, while the 

 PetroUsthes conceals itself under stones or pieces of coral, and when captured usually 

 throws off its claws. On Avalking over the coral blocks a peculiar clicking noise is heard 

 on all sides, which is found to proceed from species of Alpheus, very common in the 

 tidal pools. This noise is produced l)y the crustacean rapidly flexing the dactylus of its 

 larger chela against the corresponding immobile finger, probably under the stimulus of 

 fear, for the movement is very freely indulged in Avhen the animal is handled. Near 

 high-water mark, in places where slight pools are left by the tide, a minute hermit-crab 

 {Diogenes, sp.), scarcely a quarter of an inch in length, is very common, and here and 

 there on the sandy shore colonies of Canobita riigosa have established themselves, in 

 company with the ubiquitous Ocypods. In a tidal backwater, which forms shallow 

 lagoons at intervals round the island, the burrowing Gelasimus anmtlipes is seen in 

 great numbers, and, on sand- or mad-banks, Scoplmera mtjctiroides, a species of similar 

 habits. 



The great wealth of animal life on tlie reef is veiy apparent, for on a calm day, with 

 no breeze to ruffle the surface, and witli merely a few feet of clear water intervening, 

 the growing coral can be readily examined from a boat, wlien it is seen to be arranged 

 in irregular patches of varying size, often brightly coloured, and separated by spots of 

 coral sand. Under favourable conditions objects even of moderate size can be readily 

 discerned, the most conspicuous bcnug Actiniae, Asterids, Echini, large Molluscs, such as 

 Pterocera, Ci/prcea, &c., and gaudily-hued fishes. The most satisfactory mode of 

 collecting is by means of diving; practised divers have no difficulty in loosening large 

 blocks of coral, and in bringing these to the surface, whence tliey are drawn into the 

 boat. In this way large numbers of crustaceans are taken, either hiding in the crevices 

 or clinging to the coral branches. The genera most numerously represented are : — 

 Chlorodius, Leptodius, Etisus, Pilumnus, Trapezia, Polyonyx, Alphcns, and Gonodactjilns, 

 but a list of even the commoner species would occupy more space than (;an be allotted 

 to it here. Very interesting and varied are the modes by which most of these are 

 protected in this densely populated area, where the struggle for existence must neces- 

 sarily be severe. The slow inactive Maioid forms are frequently rendered inconspicuous 

 by heterogeneous collections of foreign objects, sucli as sponges, corallines, liydroids, &c. 

 attached to the carapace or legs, the retention of which is, in some cases, facilitated 

 by the presence of short hooked hairs. Some specimens of Micippa appear, howevtn-, to 

 content themselves with a simple coating of sand-grains whicli are entangled in or held 

 by the short hairs on the upper suil'ace. The well-known habit possessed by many 

 Droraiids, of seeking protection under an enveloping sponge or ascidiaii, which is 



