94 FOOTE : GEOLOGICAL STRUCTURE OP THE EASTERN COAST. 



From the materials thrown up into a dyke near the light-house at 

 Subfossil shells from Masulipatam, a considerable number of subfossil 

 Masulipatam. shells were collected by me. The following is an 



incomplete list of the genera obtained from the sandy clay : — 



Pyrazus. 



Potamides. 



Nassa. 



Nerita. 



Yalvata. 



Paludina. 



Lymncea. 



Area, 3 sp. 



Cultellus. 



Solen. 



Tellina. 



Mactra. 



P kolas. 



Ostrea, 3 or 4 sp. 



The swampy flats near the coast abound in shell-fish ; those within 

 tidal influence show brackish-water forms, as Poi amides, and those fur- 

 ther inland purely fresh-water forms, as Paludina and Planorbis, some- 

 times in enormous number. 



The eastern part of the delta has a sandy surface ; the western part 

 is covered with dark black washed up regur (cotton soil) . The boundary 

 line between the two runs through Weeyoor in a north-easterly direction. 

 My attention was drawn to this by Lieut. -Colonel Hasted, R..E., who also 

 informed me that this boundary is distinctly marked for a long distance, 

 the western edge of the sands forming a slightly elevated ridge across 

 country. It would be very interesting to ascertain whether this dis- 

 position of the sands depends in any way on wind action, or can be 

 connected with the great tidal waves which have at long intervals 

 devastated the delta, as in the terrible cylcone of 1864, when the sea 

 water rushed inland for a distance of over 15 miles. 



Considerable changes have taken place in the form of the coast line 

 within the memory of living men. There is a marked difference 

 between the lines laid down by the surveyors from whose survey sheet 

 95 was compiled and the lines ascertained a few years since by the 

 officers of the Madras Revenue Survey. As might be expected, the 

 delta is advancing on the sea, and would do so much faster but for the 

 very powerful coast currents which flow up or down according to whether 

 ( 94 ) 



