SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 53 



Anoplotherhan Bravard [non Cuvier) ; Monogr. de los terren. eoc, etc., 



1858. 

 Anchitherium Burmeister [iion v. Meyer) ; Descr. phys. de la Repub. 



Argent, T. Ill, 1879, p. 479. 

 Anisolophus Burm.; Anales del Mus. Nac. de Buenos Aires, T. Ill, 1885, 



p. 172. 

 DiadiapJi07'ns Mercerat, in part; Rev. del Mus. de La Plata, T. I, 1891, 



p. 458. 

 Oreomeryx Mercerat, in part; Ibid., p. 465. 

 Anomodontheriiiin Mercerat; Ibid., p. 461. 

 Thoathermm Mercerat [iioii Amegh.) ; Ibid., p. 455. 

 Diaphragmodon Mercerat; Ibid., T. Ill, 1893. 

 Diadiaphorus Lydekker, in part ; Anales del Mus. de La Plata, T. Ill, 



1893. 

 Tichodon Amegh.; Enum, Synopt. de Mamm. Foss. de Patagonie, 1894, 



P- 43- 

 Heptaconiis Amegh.; Ibid., p. 44. 



Though closely allied to DiadiapJiorns, this genus comprises smaller 

 and more slenderly built animals and differs in many details of dental and 

 skeletal structure from that genus. As the more salient characteristics 

 may be noted the following features. ( i ) In most of the species the second 

 upper premolar has the inner ridge divided into cusps, while p^ and p- 

 have a small, though distinct postero-internal cusp (tetartocone). (2) The 

 upper molars have the internal cusps well separated, but in m- the hypo- 

 cone is usually absent or indistinguishably fused with the posterior cingu- 

 lum. (3) The last lower molar has a small talon and a very small postero- 

 internal pillar, which is still smaller in m^ and niy. (4) The nasal bones 

 are much longer than in Diadiaphorus. (5) The limbs and feet are much 

 more slender and elongate than in the latter. 



Denfition (Pis. VII, figs. 10, 11; VIII, figs. 2-8; IX, figs, i-io; X, 

 figs, 1-5, 7-15). 



A. Upper Jaw. The single incisor is a caniniform tusk, resembling that 

 of Diadiaphorus and Licaphriuin in form, but varying considerably in 

 size in the different species and almost certainly also in the two sexes. 

 A long diastema separates the incisor from the first premolar, which is 

 small and two-rooted, with compressed conical crown, and internal ridge 

 even less developed than in Diadiaphorus. The second premolar has 



