Chap. VI.] trichinopoly district — ootatoor group. 93 



of the lower beds, including A. Mantelli and N. pseiido-elegans occur still, but the majority of 

 the Cephalopoda have'disappeared, and,' 'N. Huxleyanus (a^charao- 



' auna o uppoi e 3. teristic Trichinopoly form, previously met with in the grits of 



Shutanure) appears in vast numbers associated with A. Gautama, also a common Trichinopoly 

 form, and occurring occasionally in the clays of the lower part of the Ootatoor Group. An Ostrea, 

 probably identical with 0. carinata, two species of Gryphcea resembling O. vesicularis and G. 

 columba respectively, and a Cardium having more resemblance to the living C. edule than to any 

 Cretaceous species with which I am acquainted, are, with the large Area previously mentioned, 

 among the most abundant of the bivalves, and with these are associated many smaller forms, 

 Gytherea, Astarte, &c., which, like those of the Acteonella beds of Kolokaunuttom, strongly 

 resemble, and are probably to some extent identical with, species of the Trichinopoly Group. 

 Among the univalves a large species of Pleurotomaria is very abundant, and the limestones are 

 crowded with Natica, Fusus, Rostellaria, Turritella, and Valuta, also resembling Trichinopoly 

 forms. 



Excellent sections of these beds are exposed in the nullahs to the West of Coonum and 



Mineral ehai-actera of upper Permalpolliam, and specially in that half way between the two 

 ^^^^- villages which cuts directly across the strike of the beds. The 



beds consist of laminated white and pink clays, with bands of fossiliferous shale, limestone 

 and conglomerate, the whole dipping 8° or 10° to the East. South of this nullah the 

 beds strike round to the South-east as far as Moonglepaudy, and there again turn to the 

 South-west and S. S. "W., becoming nearly unfossUiferous beyond Audanore, 



Most of the fossils met with between Audanore and Coonum are confined to the limestones 



and calcareous shales. The beds of sandy clav which are laro-elv 



Distribution of fossils accord- _ •' •' "■•■o^'-j 



ing to mineral ciiaracter of intercalated are here, as elsewhere, comparatively unfossiliferous 



l)eds. J . . . . ' 



and it IS interestmg, as bearing on the question of drifting, that 



such fossils as do occur in these finer beds are pelagic Cephalopoda, (Nautilus and Ammonites,) 

 which have probably been originally deposited on those spots where they are now imbedded. 

 Nautilus Huxleijanus, A. Gautama, (which here attains a diameter of 2 feet and upwards,) two 

 or three species of the Rhotomagensis section of Ammonites, and one apparently of the section 

 Macrocephali, especially characterise certain clay beds, enclosed in calcareous concretions. These 

 specimens are perfect as imbedded, though sometimes slightly crushed, and have the mouth 

 and body whorl well preserved, but owdng to the tendency of the concretions in which they 

 are enclosed to split across, they can rarely be extracted entire. Some of the Nautili have 

 the shells very beautifully preserved, exhibiting the finest strise of growth, but most of the 

 specimens are in the form of casts. 



North of Coonum the distinctive characteristics of higher and lower beds can no longer be 

 Beds North of Coonum. traced, and the Ootatoor beds as far as Poothoor, consist of irregular 



alternations of the various beds I have described, in which we 

 meet with but small and few representatives of the remarkably rich fauna characterising the 

 beds around Odium, and those few indiscriminately distributed. The discordance between 

 the strike of the bedding and that of the boundary of the group stUl obtains as far as Andoor ; 

 the strike of the upper beds being nearly coincident with that of the base of the Trichinopoly 

 Group, while the average dip of the bedding remains pretty constant. The base of the Tri- 

 chinopoly Group and the Ootatoor beds below are exposed in the nullah North of this village, 



