336 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 28, 



face of Minora Point exhibited the following details in a descending 

 order : — Conglomerate 60 feet ; sandstone 3 feet ; bed composed 

 almost exclusively of Ostrese 2 to 4 feet ; sandstone 5 feet, at base be- 

 coming highly calcareous, and there containing innumerable Turri- 

 tellse ; lastly a fine-grained sandstone extending to the base of the 

 cliff, in which no fossils were apparent. 



Minora Point is connected with the Hala Range about 25 miles 

 distant, in the direction of Cape Monze, by a narrow bank of dry 

 sand, which alone separates the present harbour from the open sea. 

 On the eastern side of the harbour there is also a dry bar of sand, 

 stretching from Clifton towards Minora Point. Within the harbour 

 there are mud flats* covered by water at each tide, abounding with 

 three species of Cerithium, one of which I recognized as being also 

 common at the mouth of the Ganges. In the deep water Placuna 

 jplacenta is most abundant, and has been fished for from time im- 

 memorial on account of the pearls often found in the shells. An 

 island close by is covered to the depth of four or five feet, and to an 

 extent of two acres or more, with shells accumulated in this way. 



At present no river discharges itself into the harbour, the channels 

 affording little water unless during falls of rain, which I was told take 

 place about once in four years ; but there is every reason to think 

 that a branch of the Indus at one time discharged itself here. The 

 general shape of the harbour with its bars and mud flats is favourable 

 to this idea. About half a mile to the westward of Minora Point in 

 the direction of Cape Monze, the action of the sea and wind on the 

 beach has laid bare a stratum of black clay containing vast numbers 

 of oysters and broken Cerithia belonging to the species now living in 

 the harbour. At flrst I was inclined to consider that this was a post- 

 pliocene formation, but I remarked that an inshore wind, or sea-breeze 

 as it is called, prevails for a great portion of the year, and blows at 

 times with considerable violence. This wind is constantly drifting 

 the dry sand into the harbour and filling it up, the discharge of water 

 every tide no doubt again carrying out a portion of the sand thus 

 drifted. The sea however is gradually gaining on the harbour, and 

 will continue to gain on it by the gradual drifting forward of the sand 

 belt, and I have no doubt that the stratum of black clay with Ostrese 

 above noticed, was at one time within the harbour and formed a 

 portion of its flats. On the land side the harbour is also gradually 

 filHng up from the quantity of detritus carried into it by every fall 

 of rain, which remains wherever it is left by the temporary flood. 

 There is now no river affording a constant supply of water to carry 

 forward such a deposit, and it is affected only by tidal action, which 

 is not sufficient to keep the harbour open. The sea opposite the 

 mouths of the Indus is, as is well-knowTi, shallow, and it is also shal- 

 low opposite Kurrachee. At Clifton, on the eastern side of the harbour, 

 at low-water mark, I found the broken stems of trees with roots in 

 their natural position. The grain of the wood was still perceptible, 

 but Pholades had pierced it in all directions and were still domiciled 

 in it. 



* The flats are generally covered with a species of mangrove, Mgicerm fragrans. 



