the Eastern Portion of the Basaltic District of India. 551 



surface, having silicified shells distributed throughout its substance, or projecting from its surface. 

 The chert is deeply imbedded in the nodular basalt, from which it projects in some places several 

 feet. The finest specimens of Unio occur in a beautiful gray chert, imbedded in the basalt, or resting 

 immediately on it, the under surface being plain and smooth, while the upper is rough, from por- 

 tions of the large shells which project from it. On breaking up one of these masses, it was found 

 to contain entire Unios, many of them having the valves connected and closed, or partially open ; 

 the interior being filled with the same chert, spotted with fragments of shells, minute univalves, 

 and fine specimens of the two species of Cypris, which occur so abundantly. Some parts of the 

 rock exhibit a mixture of sand, clay, and fragments of shells, of very moderate hardness; but the 

 greater portion consists of chert, the materials of which are occasionally arranged in a beau- 

 tiful, light blue, enamel-like substance, around irregular cavities containing crystals of purple 

 quartz. Some portions also exhibit a minute vesicular structure ; and the whole appearance of 

 this beautiful rock forcibly impresses the mind with the conviction, that it owes its present appear- 

 ance to the action of the great basaltic eruption, which has enveloped it and the organic remains. 

 The greater number of the shells are converted into chert, but a few retain their original structure ; 

 and in some instances the calcareous matter has been converted into crystals of calcareous spar. 

 Many internal casts of entire shells are found in the substance of the rock, to which they are 

 united at a few points only, a greater or less space being left unoccupied ; in others, the entire 

 shell is converted into siliceous matter, retaining the appearance even of the ligaments unaltered ; 

 and fortunately, in a few cases, the hinge and teeth are excellently preserved. 



Numerous fragments of shelly rock, differing much in appearance, lay scattered about over 

 the table-land ; consisting partly of a fine blood-red chert, like that above described, and con- 

 taining the same shells. The gray chert was more sparingly distributed, and the Unios did not 

 occur in the other fragments. Some of them, composed of a tough white clayey stone, so soft 

 as to soil the fingers, contained Physae, Paludinae, and Limnese, mostly converted into calce- 

 dony, but others also retained their original structure, and effervesced with acids. Portions of 

 charred vegetable matter, resembling small fragments of grasses and reeds, occurred in these and 

 the harder cherts. Other specimens are composed of a greenish blue crystalline mass, resembling 

 an ore of copper, (but it is of low specific gravity, and contains no trace of that metal,) and the 

 shells contained in them are converted into the most beautiful crystalline quartz, retaining the 

 form of every convolution of the Physae and Paludinae. The cells of this stone are often coated 

 with fine silky crystals. Masses of a hard coarse chert, consist almost entirely of Gyrogo- 

 nites, but contain many of the same Physae and Paludinae. This rock appears to have formed beds 

 of about half a foot in thickness; but it was not discovered in situ. A stratified rock was however 

 found in the neighbourhood, resembling some specimens of the argillaceous limestone of the dia- 

 mond districts, but consisting of a compact whitish chert, which contained Paludinae, and the finest 

 specimens of Gyrogonites. (Plate XLVIl., fig. 1.) Night prevented the connexions of this rock 

 from being determined : the strata were, however, ascertained to be of considerable extent, and 

 to be much buried in the soil ; there were also numerous fragments of siliceous rock, partly 

 converted into a black bituminous flint, or a coarse quartzose rock, partially altered into calce- 

 dony, by which most of the shells were also replaced. 



The masses of red chert protruding from the basalt contained, besides the Testacea, small por- 

 tions of silicified wood, and what I consider to be the fragment of a bone, and of the tooth of a 

 mammiferous animal. The specimens, however, are too imperfect to admit of any certainty as 

 to what they really are ; but it is not unlikely that such remains should occur, and I therefore 

 do not suppress what may lead to a more successful inquiry. 



