AMEGHINO'S DISCOVERIES 399 



have partially been accepted also by Dr. Both,* who has 

 personally studied the problems on the spot. 



As regards the mammalian remains contained in the Santa 

 Cruz terrestrial beds, Professor Scott f was greatly struck 

 by the strangeness of the assemblage. Not a single genus 

 occurs in any part of the northern hemisphere. Some of the 

 orders even of mammals are distinct from those of the 

 northern faunas. Thus the beds have yielded no carnivores, 

 no modern groups of ungulates nor elephants, while the 

 rodents all belong to the section Hystricomorpha. The place 

 of the carnivores was taken by carnivorous marsupials, some- 

 what resembling the Tasmanian wolf (Thylacinus). Numbers 

 of small plant-eating marsupials, of which Caenolestes 

 (see p. 350) is an interesting survival, likewise occur. One of 

 the largest, most varied and most characteristic elements of 

 the Santa Cruz fauna are the edentates. They are repre- 

 sented by the Dasypoda or armadillos, the greater part of 

 whose skin is strongly ossified, the scutes forming a great 

 shield over the body, and by the Glyptodontia and the Gravi- 

 grada. The last two groups are now extinct. The glyptodonts 

 resembled armadillos, except in so far as the bony scutes were 

 joined into a solid mass like the shield of tortoises, while the 

 Gravigrada or ground sloths were extraordinarily varied and 

 numerous. Only a single genus (Necrolestes) of Insectivora 

 has been obtained in the Santa Cruz beds, as already alluded 

 to (p. 246). At present this order is quite unknown in 

 South America. The ungulates belong to the extinct groups 

 Toxodontia, Astrapotheria and Litopterna. The toxodonts 

 were represented by the genus Nesodon which somewhat re- 

 sembled a rhinoceros in shape and had similar teeth. Of the 

 second group very little is as yet known, while the Litopterna 

 are the most remarkable of all the hoofed animals. Without 

 being in any way related to the horse-tribe, certain genera 

 have paralleled the structure of the horse-foot in a most 

 wonderful way, giving the latter a striking and deceptive re- 

 semblance to that of the ancient Hipparion. The animals 

 afford, indeed, as Professor Scott remarks, one of the most 



* Both, S., " Sedimentablagerungen in Patagonien." 



t Scott, W. B., " Mammalian fauna of Santa Cruz," pp. 242247. 



