Prof. E. Forbes on Fossil Invertebrata from Southern India. 1G7 



species of the same genera in Europe. This may be said of the examples of Venus, 

 Mactra and Psammohia, genera in which the characters, so far as form is concerned 

 are not likely to present extreme modifications at any epoch. The same is true 

 of Cardita, Pinna, Avicula and Spondylus, associated in the Pondicherry beds. 



The few Echinodermata in the collection lead to similar conclusions. The spe- 

 cies of Holaster and Nucleolites are characteristically cretaceous forms, and though 

 the Brissi are perhaps most nearly allied to described tertiary species, there are 

 others not very far removed in European cretaceous beds. The few Zoophytes 

 are such as to lead to no conclusion of importance either one way or the other. 



Were these beds tertiary or bordering on tertiary, in such a tropical region, we 

 should expect to find examples of genera still abounding there, and common in 

 tertiary strata of more northern latitudes, — examples of Conus and Pleurotoma for 

 instance ; but there are none. Moreover, admitting for a moment their tertiary 

 origin, we might reasonably expect that the species in the collection identical 

 Avith described forms would, if anything, be identical with the tertiary forms found 

 in the Cutch beds ; but it is not so. The collections of Captain Grant and Captain 

 Smee furnish no identifications. We find them all in cretaceous strata as far away 

 as Europe. 



But though the closer we inquire into the evidence afforded by these fossils of 

 the age of the beds in which they are contained, the more clear does it become 

 that they are cretaceous, we have still to seek a reason for that mixed creta- 

 ceous and tertiary fades presented by the assemblage at first glance, and which 

 led to doubts respecting the epoch of the Southern Indian strata. It doubtless 

 depends on the greater development of generic forms, which though, as we have 

 seen, with only three exceptions, also known in cretaceous strata in Europe, 

 are yet so rare with us and so comparatively prevalent in the Indian beds, whilst 

 many of them are familiar as characteristic of tertiary beds in Europe, that we are 

 naturally inclined at first sight to associate with their presence the notion of a 

 tertiary origin for the beds in which they occur. It appears to me that the right 

 inference from their presence (since not one of the species is identical with any 

 known tertiary form) is, not that the deposits containing them are either tertiary 

 or necessarily connected with tertiary, but that the genera in question commenced 

 their appearance or attained a great development 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 dis- 

 appeared or have few representatives in the seas of other geographical regions, is 

 exactly what w^e should expect, a priori, to find. TJiis fact would go far to sup- 

 port the theory, that genera, like species, had geographical birthplaces, as they 

 have geographical capitals or centres. 



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