BY H. LEIGHTON KESTEVEN. 455 



To the palaeontologist this group should be of particular 

 interest as throwing light on the vexed question of the age of 

 the deposits in which they are found. 



A. E. Ortmann (25, 303), compares the Patagonian with Euro- 

 pean fossils, and then compares the former with Australian and 

 New Zealand fossils, and says : — 



" The result of the foregoing consideration is : We regard the 

 Patagonian beds as of Lower Miocene age; contemporaneous dejjosits 

 are found in the southern hemisphere^ not only in Chili (within 

 the Navidad series), hut also in Nevj Zealand ( Pareora beds of 

 Hutton) and Australia.'^ The italics are in the original. The 

 Australian beds referred to, are apparently those from which the 

 fossils under discussion are derived. 



As a support to the "Lyellian percentage" method of estimating 

 the age of a deposit, the broader comparison of the genera con- 

 tained therein, with those from deposits of determined age, 

 and with recent representatives, should give more satisfactory 

 results than would a comparison of the species in detail. For 

 this purpose the genus Lotorium, being well represented, is of 

 especial value to the Australian palaeontologist. Thus, if we 

 compare this genus as it occurs in the lower Australian strata 

 with European Miocene representatives, we are presented with 

 two entirely different types of the genus. The predominating 

 feature of the Australian section — that of the extinct Antarctic 

 group — finds expression in only one European fossil (Z. tarbel- 

 lianum). Again, if the two groups be compared with the recent 

 representatives, it will be seen that the European section has the 

 general facies of the recent species, whilst the Australian fossils 

 can, with one exception, be onl}- compared inter se. L. quoyi and 

 the Australian fossils possibly referable to its group are from 

 more recent deposits than the parkinsonianu7n-gYO\x^. These 

 facts, namely, that the predominating feature of the Australian 

 grouj? is that of an extinct section, and that the European group 

 has the general facies of the recent species, assuredly point to the 

 greater antiquity of the Australian fossils. 



