330 MR. J. E. HENDERSON— A CONTEIBUTION 



where it probably burrows in tbe soft bottom, and thus differs strikingly in habit from 

 its marine congeners. Four terrestrial species are cbaracteristic of the marshy grass- 

 grown flats which skirt the backwater, all of them belonging to the group Catometopa 

 of the Bracbyura. The most abundant of these are Sesarma quadrate/, seen running in 

 and out of its burrows at all times, and the larger Carclisoma camifex, which lives in 

 colonies, and is apparently very common, though the animal itself is rarely seen, as it 

 emerges from its hiding-places only by night. The latter species is occasionally met 

 with at some distance from the water, and its underground dwellings, unlike those of 

 most land-crabs, do not pass vertically downwards for the first part of their course ; they 

 also lack the neat and finished appearance of the external opening, seen in the burrows 

 of most Telphusse. The two remaining species, Metasesarma Bousseauxii and Metaplax 

 distinctns, are less frequent ; the former is by no means uncommon at Ennore, while 

 the latter is more sparingly met with, and I am unable to state whether it, like the 

 others, seeks protection from its enemies by hiding underground. The backwater 

 fauna is one that will amply repay investigation, and in Crustacea much has still to be 

 done before the commoner species are even approximately known. 



No collecting-ground in the Indian Seas can show a greater profusion of animal 

 life than the Gulf of Manaar, between India and Ceylon, famous for its pearl 

 fisheries. At various times many interesting zoological discoveries have been recorded 

 from this area, and within recent years valuable collections in most of the Invertebrate 

 groups have been formed by Mr. Thurston, of the Madias Museum. The Crustacea 

 which he has entrusted to me for examination were collected chiefly at Rameswaram 

 Island, Tuticorin, and the Pearl Banks on the Ceylon side of tbe Gulf (Muttmvartu Par, 

 Silavaturai Par, and Cheval Par), including many of the most interesting species referred 

 to in this paper. In the summer of 1889 I spent about three weeks in the first of these 

 localities, and for the opportunity which I thus enjoyed of collecting there I am largely 

 indebted to my friend the Setupathi, the Rajah of Ramnad, who not only placed at my 

 disposal his bungalow at the village of Pamban, but also provided me with boats and 

 efficient native divers. The island of Rameswaram, famed for its venerable temple — 

 the resort of large numbers of Hindu pilgrims — forms the first link in the chain of 

 islands and sandbanks Avhich, known as Adam's Bridge, stretches from the mainland to 

 Ceylon. To the naturalist it presents special interest from the fact that a fringing coral 

 reef appears at intervals along the coast, and the marine fauna is consequently both 

 rich and varied, while a few miles to tbe south there is a series of smaller but ' more 

 completely reef-bound islands. As a rule, even outside the reef, there is complete 

 absence of the swell or surf so characteristic of the Coromandel coast, and during either 

 monsoon one side of the island at least is sheltered and the sea smooth. Remarkably 

 shallow water is met with on all sides, and within a mile or so of the shore tbe depth 

 probably nowhere exceeds five or six fathoms ; on the outer portion of the reef, where 

 the living coral is most abundant, there is usually not more than from ten to fifteen feet 

 of water. The tidal zone varies considerably, both in character and extent. Within the 

 reef it forms a belt, perhaps averaging fifty yards or so in width, exposed at low water, 

 and then bounded by the still submerged growing coral, while elsewhere it consists of a 



