Chap. II.] alluvial deposits and blown sands. 33 



Most of the species found sub-fossil at Kandyamallur were also 

 collected by us, either living- or quite fresh, on the adjoining coast, and 

 in the creek and back-waters at the mouths of the Coleroon, Vellaur, 

 and Guddalam. Indications of a similar deposit, a few miles west of 

 Cauverypatam, in Tanjore District, have already been adverted to. The 

 sands along the coast are generally quartzose, but here and there, as at 

 Fort St. David and Cauveiypatam, there is a considerable quantity of 

 black mag^netic iron sand, and, at the latter place, a patch, several square 

 yards in extent, of red garnet sand, was noticed. 



The hloion sands north of the Pooniar extend up to Pondicherry. 

 The coast ridge from the northern mouth of the river up to the fishing 

 village of Pylittel is more than usually elevated, averaging about 25 feet. 

 It is separated from the large fiat of sand, which extends to beyond the 

 high road, by a little valley, now under wet cultivation, which would 

 appear formerly to have been a back-water. The same thing also occurs 

 on the island between the two branches of the Ariankuppam river, both 

 of which, as well as the southern arm of the Pooniar, were, when ex- 

 amined, closed by a bar of sand, thrown up by the heavy surf which pre- 

 ^^ils on this coast. 



(^55) 



