168 Prof. E. Forbes on Fossil Invertebrata from Southern India. 



Respecting the relative ages of the three deposits (Pondicherry, Verdachellum 

 and Trinchinopoly) in which the species described have been collected, two of 

 them, Verdachellum and Trinchinopoly, appear to belong to a different epoch of 

 the cretaceous sera from Pondicherry. The two former have several species in 

 common (and those species among the most prolific in individuals) which are not 

 found in the third. In them are found most of the species identical with European 

 forms. In several of the genera, found at Pondicherry as well as at the places 

 named, the forms are altogether distinct ; although, judging from the evidence 

 afforded by mineral character and association of species, the conditions of depth 

 and sea-bottom at the time of the deposition of the strata seem to have been the 

 same. The difference therefore must have depended on a representation of species 

 by species in time and not in depth. 



The beds apparently contemporaneous, viz. Trinchinopoly and Verdachellum, 

 may be regarded as equivalent to the upper greensand and gault. The European 

 species they include are either characteristic upper greensand and gault forms, or 

 else such as occur in those strata. The new species they contain are either closely 

 allied to known upper greensand or gault species, or peculiar to the Indian beds. 

 On the other hand, the Pondicherry deposit may be regarded as belonging to the 

 lowest division of the cretaceous system. In it almost all the fossils are new. 

 Such as are analogous to known species are allied to fossils of the lower greensand 

 of English geologists, and Neocomien of the French. In the genus most developed 

 in this deposit, viz. Ammonites, three-fourths of the species belong to sections 

 especially characteristic of the " Lower Neocomian " of the Mediterranean basin, 

 whilst of the remainder as many representatives of oolitic fossils occur as of upper 

 greensand species. The resemblance between many of the Pondicherry Ammonites 

 and those of Castellane in the south of France is very remarkable. 



Considered in regard to the distribution of animal life during the cretaceous 

 epoch, this collection is of the highest interest. It shows that during two succes- 

 sive stages of that sera, the climatal influence, as affecting marine animals, did not 

 vary in intensity in the Indian, European and American regions, whilst the later 

 of the two had specific relations with the seas of Europe which are not indicated 

 by the earlier. The cause of this remarkable fact is not to be sought in a more 

 general distribution of animal life at one period than at another, but rather in 

 some great change in the distribution of land and sea, and in a greater connexion 

 of the Indian and European seas during the epoch of the deposition of the upper 

 greensand than during that of the lower. 



The fact, that of the few species found in these Indian cretaceous beds which are 

 common to analogous beds in distant regions, the majority are such as have a great 

 vertical range, supports the law pointed out by M. de Verneuil and Count D'Ar- 



