SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 63 



Proterotherium australe (Burmeister). 



(Plates IX, Figs. 7, 8 ; X, Figs. 2, 3, 14.) 



Anchitherutm australe Burmeister; Descr. phys. de la Repub. Argent., T. 



Ill, 1879, p. 479. 

 Anisolophus aiistralis Burmeister; Anales del Mus. Nac. de Buenos 



Aires, T. Ill, 1885, p. 172. 

 Proterotherium australe Amegh.; Enum. sistem., etc., 1887, p. 19. 

 Diadiaphorus australis Mercerat; Rev. del Mus. de La Plata, T. I, 1891, 



P- 459- 

 Anisolophus Burmeisteri McrctVdX; Ibid., p. 464 (fide Ameghino). 



Proterotherium cingulattmi Amegh.; Rev. Argent, de Hist. Nat., T. I, 



1 89 1, p. 296. 



Proterotherium angulatum Amegh.; Ibid., p. 345 (typographical error). 



Proterotherium curtidens Amegh.; Ibid., p. 296. 



Proterotherimn mixtum Amegh.; Enum. Synopt., etc., 1894, p. 39. 



This species is apparently not represented in the Princeton or New York 

 collections save by one imperfect skull in the former (No. 15,368), and the 

 present account is chiefly derived from the descriptions and figures of 

 Burmeister and Ameghino and from the casts sent me by the latter. The 

 type specimen is a fragment of the upper jaw, with six of the grinding teeth 

 (p--m-) in place, but these teeth are broken and lack the outer wall ; they 

 show, however, the essential features of the pattern. I am inclined to refer 

 to the present species such representatives of the genus as are of moderately 

 large size and have the postero-internal cusp (tetartocone) well developed 

 in p- and -, while in m- the postero-external cusp is considerably nar- 

 rower than the antero-external and the postero-internal (hypocone) is 

 wanting. The presence or absence of a cingulum, which Ameghino em- 

 ploys in the discrimination of species, is a very untrustworthy criterion 

 and, I believe, is quite without value in this group. 



The definition of P. australe given above is necessarily quite elastic and 

 permits the inclusion in the species of a considerable range of variation 

 both in size and in the minor details of the molar-pattern, but no greater 

 in either respect than Allen has shown to exist in the recent Ursus ameri- 

 canus (loc. cit.). 



In the following table of measurements No. 6 is a cast of the type speci- 

 men of P. mixtum, No. 21 of /'. curtidens, and No. 5 of the co-type of 



