262 MAMMALIA. 



separated by a diastema both from the incisors and the premolars; the 

 foremost premolar is also isolated, with a simple conical crown ; the 

 remaining six teeth are in close series, the two premolars being conical 

 and laterally compressed, the molars rapidly diminishing in size behind 

 and losing the postero-internal quarter of the quadritubercular crown. 

 Behind the two enlarged incisors of the lower jaw, exactly as in Acdestis 

 (fig. 153), there are four nearly similar minvite blunt teeth, each with a 



FIG. 153. 



Acdestis oweni; right mandibular ramus, wanting hinder end, outer aspect, 

 about twice nat. size. Santa Cruz Formation; Patagonia. (After Ame- 

 ghino.) 



single root, which have been interpreted as a canine followed by three 

 premolars. [These are suggestive of the teeth named Stagodon from the 

 Laramie Formation of Wyoming, U.S.A.] The fourth premolar comes 

 next with two roots and a laterally compressed conical crown. The true 

 molars are more or less distinctly quadritubercular and quadrangular, and 

 the first molar is much larger than the others, which decrease in size 

 backwards. The palate exhibits two pairs of large vacuities, as in Cceno- 

 lestes. Epanorthus aratce and other species occur in the Santa Cruz 

 Formation of Patagonia. 



G-arzonia much resembles Epanorthus, but there is no conspicuous 

 diastema between the teeth, and the lower premolars 3 and 4, sometimes 

 also premolar 2, have a double root. 



FIG. 154. 



Abderites meridionalis ; right mandibular ramus, outer aspect, about twice nat. 

 size. Santa Cruz Formation ; Patagonia. (After Ameghino.) 



Abderites (fig. 154). These small animals are remarkable for the 

 development of a great cutting tooth in the middle of each ramus of the 

 jaw above and below. The anterior end of the cranium is unknown, but 

 the parts discovered suggest the original presence of a short proboscis. 



