Chap. VIII.] arrialoor group — trichinopoly district. 135 



Inocerarrms, Opis, Cytherea, Pholadomya, Echinida, and fossil wood in great abundance. These 

 beds rest on some sandy shales with calcareous nodules, which are exposed to a depth of 20 feet 

 in a well about a hundred yards to the Westward. Similar beds alternating with bands of cal- 

 careous sandstone, seem to form the bulk of the formation for about a mile to the Westward, 

 and are seen round the village of Nochycolum, and in some other places in the vicinity. They 

 pass downwards into the white sands,* previously described, and with Avhich they ai'e seen 

 alternating in nullah on the East of the Cuddalore sandstone outlier of Husain Nagrom. 



The beds to the East of Arrialoor consist chiefly of soft sandy shales with calcareous bands, 



the latter generally full of fragments of Inocerami. They are seen 

 East of Arrialoor. '' 



occasionally in the banks of small nullahs, but no good sections are 



exposed, and the country, as a rale, is much obscured by regur. Mr. Chas. Oldham obtained 



the following fossils from some of these beds to the South-east of Arrialoor ; 



Terebratula arahilis ? Eorbes, abundant. Inocerarrms. 



Ostrea tegulanea, Eorbes, Lima. 



Gryphcea stomatoidea,'Eorhes. Echinida, chiefly Nucleolites; very 



Spondylus. abundant. 



Pec ten. 

 Beds of the above character extend as far Eastward as the villages of Peddipolliam and 

 Maunahadoor, and they are probably continuous with the highly fossiliferous beds near 

 Ootacoil, to the North of An-ialoor. 



For 3 or 4 miles to the North of An-ialoor but little rock is met with in situ, but on the 

 ridges along which the road runs from Arrialoor towards Ootacoil, a large species of Gryphoea 

 is found in great numbers scattered over the surface. 



In several nullahs draining the Western slope of the sandstone-capped ridge North-east of 



Parchary, Cretaceous rocks are seen in the fonn of soft, yellow and 



grey shales with calcareous concretions, but generally unfossiliferous. 



Ao-ain on the high ground North of Mungalum similar beds are seen, with laminated sandy clays, 



and bands of coarse white sand, semi-consolidated and highly false-bedded. The clays contain 



numerous casts of small univalves and bivalves, which appear to have been disseminated through 



them in great numbers. The casts are sharp, and the species easily recognizable, but owing to 



the softness of the matrix are not easily preservable. Similar clays with fossil casts occur in 



Clays with casts of smaU g^'^at thickness in many parts of the Arrialoor group and appear to 



^o^^^- be characteristic of the formation. They extend for about 2^ miles 



to the East, alternating in thick banks with sands, shales, and calcareous bands : the latter 



abounding in fossils. 



In the nullah to the East of Ootacoil, (see map) these latter beds are well exposed, aiFording 

 Fossiliferous beds of Oota- one of the richest fossil localities in the formation. Nautilus 

 *^°^' Bouchardianus and N. Clementinus are very abundant here, 



with a Baculite, and several species of Ammonites: of the smaller fossils the most 

 abundant are :— species of Ceritkium, Trochus, Eotella ?, Mytilus, and Radiolites of 

 two species, the last exceedingly numerous, and in good preservation, but generally 

 wanting the inner layer of the shell. Some specimens, however, appeared to show casts of 

 the teeth, or at least of those on the upper valve. Other genera here met with are Fusus, 



* These sands, which are intercalated in the lower fossiliferous zone, should not be 

 confounded with those which form the central unfossiliferous zone. 



