1895.] SOUTH-AMERICAN MAUStTPIAL. 875 



always considered as of family rank. It forms, therefore, among 

 existing Marsupials a peculiar Family, and one which in America 

 represents the Diprotodonts of Australia, just as the DideJj>hijidce 

 do the Polyprotodonts. 



But turning to extinct Marsupials, the allies of Ccenolestes are 

 readily found. JFor among the large numbers of fossils from the 

 Santa Cruz beds of Patagonia described during the last few years 

 by Senor Florentino Ameghino, of La Plata, there are some which 

 so closely resemble Ccenolestes that no one can have the slightest 

 doubt as to their being really related to it. 



These are the Epanorthido' and Decastidce of Ameghino, and, 

 rather farther removed, the Abderitidce of the same author. - The 

 last-named have a hypertrophied trenchant last lower premolar, 

 and may for the present be put on one side. The other two, 

 however, which contain, according to their describer, some 13 

 genera in all, show a dentition which cannot be distinguished 

 from that of Ccenolestes in any character of family importance. 

 Indeed, I fail, no doubt from only having descriptions and figures 

 instead of actual specimens, to understand why Sefior Ameghino 

 distinguishes them from each other. But as the earliest named 

 family, the Epanortliidce, contains some of the forms most closely 

 allied to Ccenolestes, we may safely ignore for the present the 

 Decastidce, and speak of the fossil allies of Ccenolestes simply as 

 Epanorthidce. 



Further, after a careful examination of the characters of the 

 different fossil genera, I am prepared to say that Ccenolestes is not 

 only allied to, but actually falls into the Family, so that the 

 name Epanorthidce must be used for its recent as well as fossil 

 members. 



The best account of the fossil Epanorthidce is contained in a 

 paper by Ameghino '. published in 1893, and giving a full list of all 

 the genera and species described up to that date, with woodcuts of 

 many of their jaws and teeth. Of these woodcuts I have ventured to 

 copy two (see PI. L. figs. 8 & 9), those of the lower jaws of Decastis 

 columnaris (p. 3-41) and Parepanorthus minutus (p. 350), which 

 will show the exceedingly close alliance of Ccenolestes with those 

 long-extinct Patagonian Marsupials. 



Again, in the figures of Epanorthidce given on plate i. of the 

 same author's fine work of 1889 ^, several agree very closely with 

 Ccenolestes, notably the upper molar of Epanorthus lemoinei, drawn 

 fig. 14, which shows very well the quadricuspid three-rooted 

 character of the upper molars of Ccenolestes. 



The exact geological age of the beds in which Epanorthus and 

 its fossil allies have been found is still under discussion, and I do 

 not venture to express an opinion on the subject. Ameghino has 

 called them Middle Eocene, Lydekker Oligocene or early Miocene. 

 Further surveys will no doubt some day settle the point, but it is 



1 " Enumeration synoptique des especes de Mammiferes fossiles des formations 

 eocenes de Patagonie," Bol. Ac. Cordoba, xiii. p. 259 (1893). 



2 ' Mamiferos fosiles de la Kepiiblica Argentina.' Text and Atlas, fol. 



