SINCLAIR ! TYPOTHERIA OF THE SANTA CRUZ BEDS. 
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valid species, although some may be individual variants of species de- 
scribed in the present memoir. The collections studied, although exten- 
sive, are not sufficient to settle this point. It therefore seems best to list 
these forms separately, quoting for each the full bibliography and a trans- 
lation of the most complete description, with some of the characteristic 
measurements given by the author. 
PROT YPOT H ERIUM. 
Protypotherium diversidens Ameghino. 
Protypotherium diversidens Amegh. ; Revista de Hist. Nat., I, p. 292, 
1891 ; Enum. Syn., etc., p. 13, 1894 (listed) ; Segundo Censo, etc., 
p. 150, 1898 (listed). 
Of relatively small size. Is easily distinguished by the upper premo- 
lars which have an external vertical groove, broad on the crown but nar- 
rowing and suddenly disappearing toward the base, instead of running the 
whole length of the tooth as in the other species. Length P--M- .024 
C91, 292). 
Protypotherium diastematum (Ameghino). 
Patriarchus diastemcitus Amegh. ; Revista Argentina de Hist. Nat., I, p. 
293, 1898, Enum. Syn., etc., p. 14, 1894 (listed) ; Segundo Censo, 
etc., p. 150, 1898 (listed). 
Of the same size as Patriarchus rectus (synon. Protypotherium prceru- 
tilum ) or slightly larger, from which it is distinguished by the first upper 
premolar which is small, cylindrical and separated from the second pre- 
molar by a short diastema. The upper dental series is a little more 
arched. Length P--M- .029 ; breadth of palate at M- .018 ; at M x .0205 ; 
at PA013 (’91, 293). 
Protypotherium claudum Ameghino. 
Protypotherium claudum Amegh.; Contribucion al Conocimiento de los 
Mamiferos Fosiles de la Republica Argentina, p. 480, 1889; Enum. 
Syn., p. 13, 1894 (listed); Segundo Censo, etc., p. 150, 1898 (listed). 
This species, of quite small size, intermediate between P. prcerutilum 
and P. attenuatum , is removed from all the others by some characters of 
importance. I (i. e., Ameghino) know of it a fragment of the right ramus 
of the mandible with the two last premolars and the first two true molars. 
