60 



the living corals flourish in spite of the current, sometimes 

 running at the rate of 7 to 8 knots per hour, to which they are 

 exposed, terminates at the sharply defined land face of the 

 reef,^ the corals of which, constantly bathed by water and 

 never exposed above the surface, act as a natural breakwater 

 which breaks the force of the waves, so that, at high tide, the 

 shallow water between the reef and the shore is smooth. 

 The land face of the reef is made up almost entirely of 

 3Iadre2)ores, amid a perfect forest of arborescent sea weeds 

 and fleshy Alci/onicois which, as one rows over the reef on a 

 bright still morning, can be easily recognised as large snow- 

 white patches. Other genera — Porifes, Ccelorkiy Turbinaria^ 

 &c., occur in deeper water. (3) There is a zone, about 40 

 yards in breadth, between the reef and the shore, which is 

 covered by water at high tide, but completely exposed at low 

 tide, and made up of dead coral blocks, fragments, and debris, 

 among which branches of worn Madrepofca are most conspi- 

 cuous, broken off or rolled along from the reef, and covered 

 with low-growing clumps of brown and green sea weeds, and 

 enclosing shallow pools in which " coral fi^^hes " of brilliant 

 hue may be seen, and colonies of Oen'fhia leaving in their 

 wake a characteristic track. Many of the larger coral blocks 

 are extensively worn by the process of solution, or eroded by 

 boring mollusca and other animals. Among the crevices 

 of the eroded corals various crastacea [Gonodiictijlus, Pilum- 

 nus, &G.), find a home; and crawling on their surface, which 

 is frequently covered by erect or sessile encrusting sj)onges, 

 or hidden beneath them, Aimelids {Ampiihtome, Nereis, dc), 

 and bright-colored Planarians may be found. 



From the Paniban beach tlie sea bottom slopes very 

 gradually to a depth of 20 to 26 feet at a distance of three- 

 quarters of a mile from the shore. BetAveen the Kathoo 

 Vallimooni Eeef, marked on the survey chart as being " par- 

 tially dry at low water spring tides," and the spit of 

 mainland which terminates at Point Pdmen a boat passage 

 has been carved out by natural processes. North of Hdmes- 

 varam Island the living coral reef ft rmation is stated by the 



' In tlie recently issued third edition of Darwin's Structuie and Bistri- 

 bution of Coral Reefs, the reefs of the Madras Coast, of the Gulf of IManaar 

 and the northern part of Ceylon are not indicated on the map showing 

 the distribution of coral reefs hecause as Professor Bonny says (]). 247) : — 

 " The sea off the northern part of Ceylon is exceedingly shallow, and, 

 therefore, I have not coloured the reefs which partially fringe portions of 

 the shoi-fs an I the adjoining islets, as well as the Indian promontory of 

 Madura." 



