OP SOUTHERN INDIA. . 509 



by Mr. H. P. Blanford. The references to the three groups — Arrialoor, Trichi- 

 nopoly, and Ootatoor — have been, therefore, maintained, as likewise in the two for- 

 mer volumes. In a few cases I have noticed that these references appear a little 

 doubtful, especially where the locality lies at the boundary of two groups or 

 formation, but the error cannot be very great, and can easily be settled, when a 

 revision of the country surveyed is made possible after a general study of the 

 organic remains which the beds contain. 



The Arrialoor group proved again most prolific in species, their number being 

 106, a little more than two-fifths of the total. Erom the Trichinopoly group 51^ 

 were reported, and from the Ootatoor 69. t 



To the Arrialoor and Trichinopoly groups seven species are common, to the 

 Trichinopoly and Ootatoor six, to the Arrialoor and Ootatoor two, and only two 

 species occur in all the three groups. These are comparatively very small propor- 

 tions and show a distinctness of the faunas of the different groups, which could 

 hardly have been anticipated. 



Out of the total number (243) of species there are 29 identical with those from 

 cretaceous deposits of Europe and other countries, giving approximately 12 per 

 cent. By far the greater number of identifications is to be found among the lower 

 organized orders, which is decidedly due in part to the more reliable records we 

 possess of these fossils, :|: but in part it also appears to indicate that there formerly 

 existed a greater uniformity in the general geographical distribution of the lower 

 organised Pelecypoda, than can be proved in the higher organised orders. 



Among the identical species there are many which are by all geologists 

 regarded as the best characteristic fossils of the middle and cretaceous deposits of 

 Europe, and some of which are already known also to occur in Western Asia, Africa 

 and America, thus possessing a general geographical distribution. Among these 

 characteristic fossils deserve special notice Fholadomya caudata, Eryphila lenticularis, 

 Gardium productum, Protocardium hillcmum, Trigonia scahra^ Modiola flag ellif era 

 and typica, Inoceramus Cripsianus and lahiatus^ Radula tecta^ Fecten curvatus^ 

 Amtisium membranaceum, Vola quinquecostata and 1(Bvis^ JExogyra haliotoidea, laci- 

 niata and sub-orhiciilata^ Gryphcea vesicularis and vesiculosa^ Ostrea diluviana, 

 pectinata, carinata,ufigulata, and others. On the whole, however, the Pelecypod, 

 as well as the Cephalopod, and Gastropod, fauna of Southern India, agrees with that 

 of the so-called old continent, the American types being comparatively only very 

 few. In the course of my descriptions I have repeatedly had occasion to notice 

 that the. present geographical distribution of several of the families and genera of 

 Pelecypoda was clearly indicated already during the cretaceous period. 



It is also worthy of notice how well the geological position of many of these 

 characteristic species in Europe agrees with that in India, as may be inferred from 

 the preceding table. 



* Two of these are somewhat doubtful as to geological position, and of one species it is merely supposed that it 

 belongs to the present group ; the locality of the specimens not being ascertained. 



t Several of these are doubtful, the difficulty arising chiefly from the uncertainty of the rocks at Pondicherry, whether 

 they are Valudayur (^Ootatoor) group, or Arrialoor group. More of the fossils appear to point to the latter division. 



J Their shells being generally much better preserved than those of the higher orders. 



6i 



