Chap. VII.] trichinopoly district —trichinopoly group. 121 



and fossil wood is abundant ; some of the imbedded trunks measuring not less than 3 feet 

 Coralliferou3 conglomerate. ^ diameter. Corals also are abundant in the conglomerate to 

 the exclusion of more fragile fossils, which only occur in tEe finer 

 arenaceous varieties of the limestone. 



The limestone ridge is very conspicuous as far as Coonum, but beyond this place little is 



Lower beds— Coonum to Seen of it up to the nullah at Andoor, the surface being thickly 



Andoor. ' 



covered with regur, which also entirely conceals all the higher 



beds of the group as far South as Kurribiem. Between this latter place and PermalpoUiam 

 they are tolerably weU seen, consisting of parallel bands of coarse arenaceous and gritty 

 limestone, alternating with brown sandy shales, and dipping at angles of 5° and 6° to the 

 Higher beds between Per- Eastward. Near Kurribiem I found in some of the highest 

 mBlpoUiam and Kunibiem. ^jg^jg, in conjunction with Ammonites characteristic of the 



group, a species which in external ornamentation closely resembles A, bisulcatus, and others 

 of the Liassic Arietes section of Ammonites. Further examination is, however, requisite 

 to determine its affinities. 



In the nuUah to the North of Andoor the Trichinopoly beds are again exposed much 



diminished in breadth. A band of conglomeratic limestone fuU of 



Chemnitzia undosa, Vohitas, Natieas, and some of the laro-er 



univalves marks the base of the group, and is succeeded by shales, in which are occasionally 



imbedded gigantic specimens of Ammonites Gautama, and other Smaller species, and two species 



^ ^ ^ of NautUi. One of the first-mentioned specimens, now in the 



Geological Museum, wanting the greater part of the body 



whorl, which was too decayed to be extracted, measures 3 feet 6 inches in diameter the outer 



whorl being nearly a foot in thickness. When perfect this monster must have measured not less 



than 5 feet across. Portions of the shell still adhering to it are a quarter of an inch in 



thickness. 



These beds dip on an average about 8° E. by S. They continue to a point about half a mile 

 East of Veraghoor, where the bottom beds of the Arrialoor group, characterised by their 

 peculiar fossUs, cross the nullah. Several bands of limestone are intercalated in the upper beds, 

 showing a concretionary structure, combined with the finely laminated structure of deposition 



which evidences di-ifting of the detritus, and the small entire 

 Limestones of upper beds. n ■■ i i n i- i 



and broken shells which are enclosed, resembling the Garoodamun- 



galum limestone. A small free coiled annelid, with a straight extremity, is very charac- 

 teristic of the Trichinopoly beds in this neighbourhood, and its presence afi'ords a ready 

 means of distinguishing them from those of other groups when other characteristic 

 fossils are wanting. 



In the nullah to the East of Poothoor some of the higher beds of the Trichinopoly group 

 are seen dipping about 12° to the E. S. E ; but the regur which 



Bed8 East of Poothoor. ^^^^ ^^^^^^ ^^^ ^^^^^ ^^ ^^^ country, to the depth frequently 



of 20 feet, conceals the underlying rocks, except occasionally in the banks of some few 

 nullahs, and even in them the sections are few and bad. Still further to the North an 

 occasional gUmpse of rocks resembling Trichinopoly beds is obtained in the upper 



Northern termination of P^^ 0^ some of the nullahs draining the East slope of the 

 group not ascertainable. Purawoy ridge, but the only fossil characteristic of the group 



that I met within these beds was a keeled Ammonite, which I found in a small nullah 



Q 



