Chap. VI.] trichinopoly district — ootatoor group. 83 



Dr. Muzzy, the artificial mounds thrown up from excavations, exhibit the characteristic denuda- 

 tion of the soft Ootatoor clays. (Plate I.) 



Crossing the narrow strip of plant-beds abeady described in a foregoing chapter, the base 

 of the Ootatoor Group is met with in a small nullah about three quarters of a mile to the 

 East of the Ootatoor bungalow. The bottom of the group consists of soft brown ochreous 



clav or fine silt, similar to that which prevails over the country 



Character of beds. j ' r j 



to the Eastward, and resting on the unevenly denuded surface 



of the plant-beds. It is finely laminated, the laminaj dipping at a low angle to the Eastward, 



and is cut up in all directions by innumerable layers of a soft chalky mineral, and plates of 



gypsum running vertically through the mass. In-egular nodules of ferruginous clay, their 



cracks filled with crystallized Selenite, are also disseminated, and many of these contain N'autilw 



Ammonites, &c., the shells of which have been replaced by Sele- 



^*'^*''^* nite. A few other fossils, viz., Belemnites, Lima, Terebratula, Fleu- 



ro<o»ianfl!,Pwm«, and a peculiar conoidal coiled -Ser^M^a* also occur, but the species are few, and 

 many of them peculiar to this neighbourhood. Among the Cephalopoda, Nautili of the Radiat- 

 section are most common, and one of these appears to be identical with the European N. pseudo 

 elegans, D'Orb., of the Neocomian formation. "With this is associated Ammonites inflatus, Sow, 

 and a Samite closely allied to, if not identical with, the Gault H. armatus of the same author. 



Anomalous character of This association in the same bed of species, peculiar to three 

 ^*"'"^- distinct and widely separated zones of the Cretaceous formation of 



Europe, is characteristic of the whole Group. All these species are met with again in the beds 

 around Odium, and the varied fauna there associated with them, fuUy bears out (so far as I have 

 at present investigated it) the anomalous character, of which we have here an example. 



On the North-east, where, as above mentioned, the clays are exposed by irregular pluvial 

 denudation, these beds present much the same appearance as at 



Septaria nodules. Ootatoor. They are brown flaky silts, 'sometimes sandy, cut up 



by vertical layers of soft powdery chalk and gypsum, and full of little septaria and radiating 

 veins of impure gypsum. The Septaria are small, generally about the size of an egg or an 

 orange, and almost as regular in foiTa. They are generally rather elongated, and conical or 

 acuminated at the extremities, and apparently owe their form to that of the body which 

 has constituted their nucleus ; but after breaking many scores of them, I have never dis- 

 covered any organism, except in one case, in which a small bone was enclosed, and which was 

 evidently not the nucleus of the nodule. Nodules from the London clay, similar in form to the 

 above, were shown by Mr. WethereUf to have been formed around the horny stem of a Zoophyte 

 (Graphularia Wetherellii), the cast of which he frequently found in the interior. It is very pro- 

 bable that the nodules of the Ootatoor clay may have been formed around some similar organism, 

 the impression of which has disappeared in the subsequent shi-inking of the interior, and the 

 infiltration of calcspar and gypsum which fill the cracks of the Septarium. 



Belemnites and a few Nautili and Ammonites, with, in some places, a very small species of 



oyster, in great abundance, are the only fossils found here, but the 



OSS s o o a oor c ays. former occur in vast numbers scattered everywhere on the surface. 



The guards are the only parts preserved, and of these I have distinguished three species, but as 



* This Surpula is distinct from that which occurs at Muddam, and again at Odium, and is 

 peculiar to these clays of the lower beds, of which it is very characteristic, 

 t Quar. Journal, Geol. Soc, London, Vol. XV., page 30, 1859. 



