94 NATURAL SCIENCE. Aug., 1893. 



Ungulates, for instance, had attained tall-crowned or hypsodont molar 

 teeth, and the same was the case with the Rodents, which had likewise 

 discarded milk-teeth. Indeed, Homalodontotheviiim (we trust we have 

 spelt the name correctly) is the only form which can be regarded as 

 a generalised one ; most of the Ungulates having the digits reduced 

 to three, and the carpus of the interlocking type. The list of this 

 earliest Santa Cruz fauna, as it is termed, includes only Marsupials, 

 Edentates, Toxodonts, Typotherioids, certain aberrant and peculiar 

 types of Perissodactyles, Hystricomorphous Rodents, and Primates 

 allied to those now inhabiting South America ; and the same holds 

 good for the overlying Patagonian fauna, which has been correlated 

 with the Miocene. All the genera found in these formations may 

 accordingly be regarded as having originated in South America. 

 When, however, we reach the still higher beds of Monte Hermoso 

 and the Pampas, which have been identified with the Pliocene, we 

 meet for the first time with Tapirs, Horses, Llamas, Deer, Mastodons, 

 Murine Rodents, and true Carnivores, which are evidently immigrants 

 from North America, where they occur in strata devoid of the 

 remains of any of the above-named exclusively Neotropical forms. 

 If further confirmation be required that the connection between the 

 two halves of the continent did not take place before the Pliocene, 

 it is forthcoming by the evidence of an incursion of South American 

 Edentates into North America during that epoch. It may be added 

 that the occurrence of monkeys belonging to the Cebidae in the earlier 

 Argentine Tertiaries affords some confirmation of the view that the 

 monkeys of the Old and New Worlds have had an independent 

 origin. 



Paleontologists in the Argentine Republic have little oppor- 

 tunity for comparing their fossils with similar remains discovered 

 elsewhere, and certain unfortunate rivalries have led to much con- 

 fusion in the nomenclature even of the best-known genera and species. 

 We are thus glad to announce that Mr. R. Lydekker, under the 

 auspices of the Royal Society of London, leaves England on August 

 24, to examine the fossil vertebrata in the museums of Buenos Ayres 

 and La Plata. He goes in response to the special invitation of Dr. 

 F. P. Moreno, founder and director of the great museum in the new 

 city of La Plata ; and with his great experience of the Old World 

 fossil vertebrata, he ought to render much service to Zoology by 

 personally revising the work of his colleagues in the remote republic. 



