306 A. K. Coomdrasivdmy — Radiolaria in Gondwdna Beds. 



fragments of clastic quartz are rarely as large as the Radiolaria, 

 and graduate downwards to the finest dust. Very minute bedding 

 is clearly seen in the slides. The finer material seems to contain, 

 or to be aggregated into, small globular masses, some of which are 

 rather conspicuous, but very possibly not of organic origin. 



Dr. Hinde has very kindly examined the slides, and says "there 

 can be no doubt that the organisms are radiolaria." " Probably 

 several forms are present, most of them rounded or lens-shaped 

 discs with minute reticulate structure and without radial spines ; 

 others are oval with spines, and one form is like a sugar-loaf in 

 section." In some cases there is a body with reticulate structure 

 within a clear circular area ; this may indicate the presence of 

 radiolarian forms with the inner test better preserved than the outer. 



There are also in the slides some groups of small rounded bodies, 

 of inconstant dimensions, which, as stated above, are probably not of 

 organic origin. Dr. Hinde thinks that the disc or lens-shaped forms 

 with reticulate structure (Figs. 5, 6), which are by far the most 

 abundant forms present, belong to the genus Spongodiscus in the 

 Discoidea section. The conical perforate form (Fig. 4) probably 

 belongs to the genus Dictyomitra in the Cyrtoidea division. The 

 spined forms (Figs. 1-3) are too faintly shown for determination, 

 but may belong to the Discoidea section. 



The association of these radiolarian forms with plant -remains 

 (the shales are known as plant-beds, though the plant-remains are 

 not very abundant; I found no mollusca myself) is of great interest, 

 as the shales must have been deposited in comparatively shallow 

 water, a state of things also indicated by the detrital character of 

 the other beds included in the Sripermatur group. The shales 

 cannot, however, have been formed very near the shore. Mr. Foote 

 says that they " show every evidence of having been deposited in 

 perfectly tranquil water at sufficient depths probably to be beyond 

 the agitation of the waves. The fragmentary nature of the fronds 

 and leaves appears to indicate that they were drifted out to sea" 

 (Mem. Geol. Surv. India, vol, x, p. 64, 1873). The most porcellanic 

 shales seem to contain the best preserved plants. 



The Eadiolaria must have been present in sufficient quantity to 

 give a very siliceous character to the rock, yet the use of the term 

 ' radiolarian chert ' would hardly be justified. I might add that 

 Eadiolaria are to be found at the present day in shallow water, 

 though not in such abundance as in the open ocean. 



Finally, I desire to thank Dr. Hinde for his very kind assistance 

 and advice. Eeferences. 



Mem. Geol. Surv. India, vol. x, p. 64, 1873. 

 Paleont. Indica, ser. ix, p. 236, 1875. 

 Geology of India, 2nd ed., pp. 182, 208, 1893. 



EXPLANATION OF PLATE XVII. 



Radiolaria from Upper Gondwana Beds, Sripermatur. 

 Figs. 1-3. — Spined forms, possibly belonging to the section Discoidea ; outlines 



only distinguishable ; x 125. 

 Fig. 4. — Conical reticSate form probably referable to the genus Dictyomitra, x 420. 

 Figs. 5, 6. — Lenticular reticulate form perhaps belonging to the genus Spongodiscus, 

 X 200. 



