240 NOTOUNGULATA order viii 



molars. Upper molars almost always broader than long, consisting of an edoloph 

 and two unequal transverse ridges, and always with crochet and often also with 

 crests. Lower molars with a very short anterior crescent, an elongated posterior one, 

 and two inner cusps, of which the first is considerably extended transversely. Carpals 

 alternating. Calcaneum long, with a small, usually transverse facet for articulation 

 with the fibula. Astragalus with foramen above the flat tibial facet, the upper 

 margin of which is deeply excavated. Terminal phalanges frequently developed as 

 stout, curved claws, or as broad hoofs, ahvays fissured in front. Manus and pes 

 pentadactyl. 



The Entelonychia include medium - sized to large herbivores, and are 

 restricted to the Tertiary of Patagonia. They possess certain characters, 

 such as form and retractability of the terminal phalanges, in common with 

 the so-called Ancylopoda (now Chalicotheriidae) of Cope. On the other hand, 

 the dentition most decidedly indicates close relationship with the Toxodontia, 

 from which they are distinguished by the teeth being rooted, completely 

 enamelled, and never prismatic. The upper teeth are also almost always as 

 broad as they are long, and have a small crochet, which, however, through 

 fusion with the cusps on the inner side of the ectoloph, soon becomes in- 

 conspicuous. The lower molars are more massive than those of Toxodonts. 

 The molars usually have in addition a cingulum, which is developed in the 

 upper teeth on the anterior, posterior and often also on the inner and outer 

 margins, but in the lower molars only on the outer margin. A cingulum is 

 never present in the Toxodontia. 



The skull is known only in Notostylops, Leontinia and Homalodontotherium, 

 and in general resembles that of Nesodon. The nasal opening is, however, 

 much more deeply incised than in Toxodonts. The mastoid region of 

 Homalodontotherium is much less inflated, and the muzzle of Notostylops is 

 much shorter and more pointed than among Toxodonts. The skeleton of 

 Homalodontotherium is known only by the calcaneum, astragalus, humerus, 

 ulna and tibia, together with the manus and pes. The humerus has a well- 

 developed deltoid crest and a faint trace of the entepicondylar foramen ; it 

 is also very broad at its distal end. Ulna and tibia are quite stout, and the 

 latter at the same time very short. Manus and pes have each five digits, the 

 metacarpals are extremely slender, the metatarsals short and stout. 



3.1-0. 4. 3. 



Family 1. Notostylopidae Ainegliino. 



- A ^"^<^''i/'^'^ *'^ ^of^^ jaivs. P, P and the upper canine are 



reduced, I.y, I^ and the canine of the lower jaw ctre lacking. Premolars molariform, 

 the upper ones having, hoivever, only one inner cusp. Upiper molars much broader 

 than long, without crest but with crochet. TJie posterior inner cusp of the lower 

 molars is very weak. All of the teeth are brachyodont. Snout short and pointed. 

 Occiput broad, with inflated mastoids. 



This early specialised family has left no descendants. It becomes 



extinct at the close of the Eocene. 



3 13 3 

 Notostylops Ameghino (Fig. 325). ' ' o ' Catastylops Ameghino. With 



o* 1 . o. o. 



