Geological Society. 289 



on the banks of the Kistnah, and those on the banks of the Pen- 

 nar. Where the sandstone rests upon the limestone schist, a gra- 

 dual passage occurs. The rock is more or less compact, and its 

 prevailing colours are red and white. The diamond breccia is con- 

 sidered by the author, as only a variety of the sandstone in which • 

 fragments of older rocks have been imbedded. Ninety miles S.W. 

 of Nagpoor traces of coal were noticed, and in the hill of Won 

 (lat. 20° 6', long, nearly 79°) Mr. Malcolmson found the cast of ap- 

 parently a hollow vegetable, the only trace of an organic body ob- 

 served by him. The sandstone, as already noticed, partakes of the 

 same jointed structure as the subjacent limestone. It is penetrated 

 as well as overlaid by trap, and near Nagpoor veins of granite have 

 converted it into quartz rock. In the district drained by the Pennar, 

 the sandstone attains the height of 3000 feet, forming the horizontal 

 or flat summit of the mountains ; but in the same district, and at no 

 great distance, it occurs on a level with the plain. 



Tertiary Strata. — Masses and fragments of differently coloured 

 chert, a tough, white, argillaceous stone, and a greyish blue crystalline 

 rock, all containing freshwater shells, either project from the trap in 

 which they are entangled, or are scattered over its surface for consider- 

 able areas in the Sichel hills. In a precipitous descent, on the northern 

 flank, the author also noticed ahorizontal bed of white limestone, 12 ft. 

 thick, containing freshwater shells and resting on granite, but covered 

 by basaltic debris. The organic remains, brought to Europe by the 

 author, have been examined by Mr. James De Carle Sowerby, and as- 

 certained to belong to two species of Gyrogonites, two of Cypris, two 

 of Unio, with numerous specimens of Paludinse, Physse, and Limneae. 

 The greater part are siliceous casts, but some retain their original 

 calcareous matter. Silicified portions of palm woods, and fragments 

 of vegetables, in a charred or carbonized state, also occur. In ac- 

 counting for the diiferent state of preservation of the shells, Mr. 

 Malcolmson suggests, that the lime being in some instances retained, 

 may be explained on the supposition, that the shells were perfectly 

 dry at the time they were acted upon by the basalt. 



With respect to the origin of this singular rock, the author is of 

 opinion that the basalt, when it was irrupted, changed the features 

 of the country, and, destroying pre-existing lakes, entangled in its 

 substance the debris and shells which had accumulated at the bottom 

 of the bodies of water, and converted the loose sand into chert or si- 

 liceous rock. Of the age of the formation, he does not pretend to 

 offer a precise opinion. None of the shells have been identified with 

 those now inhabiting the rivers of India ; and he is, therefore, in- 

 clined to consider them as extinct, and to refer them to the tertiary 

 sera. 



This fossiliferous chert was noticed by the author over a surface 

 extending 140 miles N. and S. ; but shells considered to be identical 

 with those collected by him, were found by Dr. Spilsbury, iB miles E. 

 from Jubalpore (lat. 23° 45' N., long. 78° 53' E.), in a block of in- 

 durated clay, resting on basalt* ; by Dr. Voysey, in the Gawilghur 



• .Journal of the Asiatic Society of Bengal, vol. ii. pp. 205 and 583 

 PhU, Mag. S, 3. Vol. 12. No. 74. March 1838. 2F 



