326 [Jan. 31, 



long to those subgenera especially cliaracteristic of the " Lower 

 Neocomien " of the Mediterranean basin ; whilst, of the remain- 

 der, as many representatives of Oolitic fossils occur as of upper 

 green sand. The resemblance between the Ammonites of this 

 part of the collection and those of Castellane, in the south of 

 France, is very remarkable, though the specific identity of any of 

 them is doubtful. Having seen no account of the Conchifera of 

 the Castellane beds, I cannot say how far the analogy is borne out 

 among the bivalve MoUusca among the Indian species, of which 

 there are many very peculiar forms. 



5th. Considered in regard to the distribution of animal life 

 during the Cretaceous era, this collection is of the highest interest. 

 It shows, that during two successive stages of that era the climatal 

 influence, as affecting marine animals, did not A^ary 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 ab- 

 sent from the earlier. The cause of this remarkable fact is not to 

 be sought for in a more general distribution of animal life at one 

 time than at another, but rather in some great change in the dis- 

 tribution of land and sea, and in a greater connection of the Indian 

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

 greensand, than during that of the lower. To this cause must 

 also be attributed the peculiar tertiary aspect of the Indian col- 

 lections, depending on the presence of a number of forms usually 

 regarded as characteristic of tertiary formations, such as Cyprsea, 

 Oliva, Triton, Pyrula, Nerita, and numerous species of Voluta, 

 the inference from which, since not one of the species is identical 

 with any known tertiary form, should not be that the deposits con- 

 taining them are either tertiary or necessarily connected with 

 tertiary, but that the genera in question commenced their appear- 

 ance earliest in the Eastern seas, which, when we recollect that in 

 those very seas at the present day, are found the great specific 

 assemblages or capitals of those genera, whilst they have either 

 disappeared or have few representatives in the seas of other geo- 

 graphical regions, is exactly what we should expect, a priori, to 

 find. This fact would go far to support the theory, that genera, 

 like species, have geographical birth-places as well as geographical 

 capitals. 



The fact, that of the few species found in the Indian cretaceous 

 beds which are common to the same beds in distant regions, the 

 majority are such as range through several deposits of different 

 ages, supports the probability of a law which I have elsewhere 

 indicated, viz. that the range of the geographical distribution of 

 species is ustially correspondent to the range of their distribution 

 in time. 



The probability of the proposed law, that the marine faunas of 

 distant localities, under similar conditions of climate, depth, and 

 sea-bottom, maintain their relations rather by the representation 

 of forms by similar forms, than by identity of species, is also 

 home out by the examination of these collections. 



