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GEOLOGICAL SURVF.Y 



interesting monograph, in which he referred the Trichinopoly 

 and Vriddhachalam beds to the age of the upper green sand 

 or gault, and the Pondicherry beds to the neoeomian of 

 European geologists. M. Alcide D'Orbigny, the distinguished 

 French palaeontologist, from an examination of a collection 

 of fossils made near Pondicherry, arrived at a rather differ- 

 ent conclusion, and regarded the rocks as of upper creta- 

 ceous age. The deductions of each of these eminent natu- 

 ralists were justified by the materials they severally dealt 

 with, but the subsequent examination by Dr. Stoliczka 7 of 

 the whole of the superb collection of fossils collected by Mr. 

 H. F. Blanford and his colleagues showed the age of the 

 series expressed in English geological terms to range from the 

 upper green sand to the upper chalk, or to use the conti- 

 nental nomenclature from the Cenomanian to the Senonian 

 periods. Several seasons were devoted by Mr. H. F. Blanford 

 to the close and critical examination of that most interesting 

 region, and he embodied his results in an . admirable memoir 

 which appeared in 1863. Unfortunately no good maps on a 

 sufficiently large scale existed on which to lay down the details 

 of the very intricate and often very obscure and consequently 

 difficult stratigraphal disposition of the beds ; hence the map 

 accompanying the memoir can only be regarded as a sketch 

 showing the general features and representing very inade- 

 quately Mr. H. F. Blanford's elaborate mapping of the 

 country. Mr. H. F. Blanford sub-divided the South Indian 

 cretaceous rocks into three groups, the Arialur, Trichinopoly, 

 and Utatur groups, to enumerate them in descending order. 

 The cretaceous rocks as seen along their boundaries, rest upon 

 the gneissic rocks generally, but here and there remains of an 

 older series of sedimentary beds of lower Jurassic age crop 



7 The first Palaeontologist attached to the Geological Survey Depart- 

 ment as special officer. 



