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India, Sumatra and especially in Ceylun and IJorneo. Aniungst the 

 still living Bornean forms there arc found some species closely allied 

 to the fossil ones; /-•, gracilis in particular closely resembles /-*. 

 Everetti Smith from Sarawak. 



Setting on one side its dissimilarity to the fauna of the „inter- 

 trappean beds" and on the other its resemblance in one highly 

 characteristic point to the fauna of the present day we may conclude 

 that the Mclawi deposit must be of more I'ecent date than the said 

 Indian strata, which constitute a transitional formation between 

 cretaceous and tertiary. For the above reasons the Mclawi deposit 

 cannot be older than tertiary but may be of eocene age as, not one 

 of the seven aforesaid species is known to belong to the present 

 fauna and may be considered as extinct, the habitus of two of 

 these species {Melanin mclaviensis and Cijrena suUrigonalis) is more- 

 over somewhat aberrant when compared with still living forms. 

 Meanwhile a more exact determination of its age than „tertiary" 

 cannot be given with any certainty and it is for this reason and to 

 avoid all misunderstandings that I propose to call this deposit by 

 the generalizing name of „Melawi group" in reference to the region 

 where it has originally been found. 



From the material which has been examined, the Mclawi-group can 

 be traced from the S. Tempoenak below Sintang eastwards along 

 the Mclawi as far as the S. Lekawai and also on the S. Kajan to a 

 certain point somewhat above Maboek i). This tertiary (eocene?) 

 brackish-water sediment can only liave been formed with the assis- 

 tance of rivers and brooks which perhaps belonged to the same river 

 system that is now represented by the Melawi and its tributaries and 

 accordingly the beds of these streams may have been out out of 

 the sediments which they themselves have contributed to form. 



1) At present it is impossible to trace a further extentioii ol' the MClawi-gnnip. I can 

 only state that I have also received tlirougli the agency of Wing Easton a consignment 

 of petrefactions from the river Silat (flowing into the Kapoeas near Silat above Sintang) 

 which contains a fauna differing from that of the Mclawi-group. 



Tarticularly nnraerous amongst which are the remains of Vivipara which is repre- 

 sented liy at least two di Herent species and there also occurs a species of CViw/« (s. str.). 

 The latter seems to be quite distinct from 6'. dajucemis 

 while amongst the species of Fivijiunt, a highly characteristic 

 form is found which 1 propose to name f. Eculoni. Tlie 

 figures of two specimens of this new species are inserted here. 

 A very remarkable characteristic of this species is the pre- 

 sence of sharp and prominent keels, one of which situated at the angle of the whorls 

 projects very strongly. 



It is possible that this deposit of the river .Silat is older than the Mclawi-group, 

 but certainlv it is not older than cretaceous. 



