Chap. VI.] trichinopoly district — ootatoor group. 91 



ii}) ; moreover, about half a mile to the East, a little boss of gneiss, too smaU to be 



mapped, but apparently in place, protrudes through the Cretaceous beds to the surface ; 



all bearing out the conviction above expressed, that the gneiss floor of the Ootatoor 



beds is extremely iiTsgiilar, notw-ithstanding its general smoothness where the latter beds 



have been entirely denuded to the Westward. 



The above described beds are followed to the East and South-east of Maravuttoor by white, 



grey, and purple banded gypseous clays, with bands of globular 

 F0SSU3 of Maravuttoor beds. . j • i • •, 



concretions, and occasional irregular beds of calcareous shale and 



limestone, full of fossils, among which the Cephalopoda are very numerous. The Ancyloceras or 

 Hamite previously noticed, at Ootatoor (page 83), a large Turrilite allied to T. tuberculatus, Bos., 

 Ammonites latidorsatm, Mich., and A. Timotheanus, Mayor, are among the most common : 

 Ammonites Eoui/anu^, D'Orb., also occurs here. The first two of these Ammonites are un- 

 doubtedly identical with the species of M.M. Michelin & D'Orbigny from the Gault and Craie 

 chloritee of the South and East of France, and of M. Pictet from the Gres-verts of Geneva, and 

 A. latidorsatits is one of the commonest species of this part of the Ootatoor Group, where it attains 

 a diameter of nearly eight inches ; A. Rouyanus is also undoubtedly identical with the CasteUane 

 species of M. D'Orbigny, and is one of the few species which is common to the Valudayur 

 group of Pondicherry and the Ootatoor.* N. Forhesianus, Belemnites, BacuUtes, and several 

 species of Gasteropoda and Conchifera, Pleurofomaria, Sostellaria, Natica, Pecten, Area, &c., 

 are common in the same beds. 



The dip of the above beds averages from 12° to 15° E. by S. to E. S. E., and 

 Thinning out of lower beds ^^^ strike is therefore from two to three points more Nor- 

 to Nortb of Maravuttoor. ^j^erly than that of the boundary. This variation obtains 



throughout the Ootatoor beds to the East and North-east of Maravuttoor, and indicates the 

 t hinnin g out of the group to the Northwards. Accordingly when we trace the gypseous 

 clays to the North-east of Maravuttoor, we find that the non-gypseous beds beneath them 

 gradually disappear, together with the accompanying conglomerates and Limestones, and in a 

 nullah which flows to the South-east, and cuts deeply across the beds, about 2 miles from 



Maravuttoor, a mass of obscurely bedded white and purple banded 

 Gypseous clays. 



clays, full of lenticular plates of Selenite, and q[uite unfossiUferous, 



extends from the verge of the gneiss where it is first exposed to within a half mile of Odium. 



A quarter of a mile further to the North massive beds of the 

 Shell limestones. 



yellow shell Lmestone re-appear, dipping, as usual, with great 



irregularity in the neighbourhood of the gneiss, and covering the high ground with the debris 



of their out- crop. 



Similar limestones, alternating with gypseous clays and calcareous shales, form the 



mass of the beds to the West, East, and North of Odium, the 

 Fossil beds around Odium. ' 



beds which I have frequently referred to as the richest 



fossiliferous deposits of the Ootatoor Group. Not less than six species of Nautilus, between 



twenty and thirty Ammonites, and three or four species each of BacuUtes, Turrilites, Hamites 



and Ancyloceras, and one species of PtycJioceras represent the Cephalopoda alone. The 



Gasteropoda and Conchifera are equally abimdant in individuals, and probablj^ also in species 



but as they are chiefly in the form of casts, and I have as yet had no oppoiiunity of 



examining them individually, I am unable to speak to this point with any confidence. 



* See Palaeontologia Indica, Part I. 



