TO INDIAN CAKCINOLOGY. 329 



I have taken by this method, in the sheltered water of Madras harbour, several species 

 which I have not met with elsewhere. 



Stretching along the Coromandel coast, for a very considerable distance both north and 

 south of Madras, is a system of shallow backwaters or lagoons running parallel to the 

 sea-line, though often separated from the sea itself by an interval of a mile or more, and 

 joined by means of canals into a continuous waterway. In certain places the back- 

 water widens out to form large lake-like expanses, one of which, the so-called Pulicat 

 Lake, is thirty -seven miles in length. For the greater part of the year this system is 

 practically shut off from the sea, but during the rainy season the intervening sandy bar, 

 at intervals, is either artificially cut, or forced by the surplus accumulation of water, the 

 result being that the sea is allowed to enter and a certain admixture takes place. 

 Porpoises and sharks find their Avay in at this time, while sea-snakes (Hydrophidae) 

 are often extremely plentiful, and indeed may be found throughout the year. The 

 fauna is extremely rich, more especially in free-swimming organisms, and is decidedly 

 marine in character, though the water, as already stated, is more or less fresh. I have 

 taken with the tow-net large numbers of Schizopods, Lucifer, and other marine forms, 

 in places where the water was freely used for drinking purposes by my boatmen. At 

 night the surface often teems with brilliantly phosphorescent organisms, which on 

 examination prove to be mainly the smaller Crustacea. One of the best hunting- 

 grounds on the backwater is the village of Ennore, about nine miles to the north of 

 Madras, which formerly, before the hill ranges became so readily accessible by rail, 

 was a favourite resort. Here is a considerable expanse of water, bounded on the 

 landward side by low, flat, grass-grown plains, intersected by canals and creeks. In the 

 lake, as it may be termed, Scylla serrata is very abundant, and large numbers are sent 

 to the Madras market, while species of Penceus, and the swimming Grapsoid crab, 

 Yaruna litterata, are no less characteristic. The sandy or muddy shores, close to the 

 water's edge, are everywhere pierced by the narrow cylindrical holes of two species of 

 Gelasimus (G. annulipes and G. triangularis). The curious habit peculiar to the males, 

 of waving the larger claw as if beckoning, Avhich has earned for them the title of 

 " calling crabs," is by no means general in the two ahove-mentioned species ; at least I 

 have observed it on comparatively few occasions. What the object of this move- 

 ment is I am unable to say, but when I noticed it a large number of individuals were 

 simultaneously engaged in the act ; the claw which is so enormously developed on one 

 side of the body in the male sex is, in all probability, used as a hole-boring organ. 

 Locally the Gelasimi are known as "dhobi crabs," doubtless from the resemblance of 

 their beckoning movement to the manner in which the native washerman swings the 

 clothes over his head in the act of pounding them against a flat stone. One of the 

 commonest backwater Decapods is the hermit-crab, Clibanarius padaoensis, lately 

 described from the Mergui Archipelago, the young of which are found in great numbers 

 near the water's edge, and almost invariably inhabiting the shells of Cerithiids. Two 

 other hermits, both species of Ccenohita (C. rugosa and C. compressa), also frequently 

 occur, but they freely leave the water, and are often to be met with wandering somo 

 distance inland. In certain localities Alpkeus malabaricus is found in muddy creeks 



