SCOTT: TOXODONTA OF THE SANTA CRUZ BEDS. 
23I 
Adinotherium nitidum Ameghino. 
Adinotherium nitidum Amegh.; Enum. sistem., etc., 1887, p. 18. 
? Adinotherium corriguenense Amegh.; Anales del Mus. Nac. de Buenos 
Aires, T. XVI, 1907, p. 77. 
The only definite character which distinguishes this species is its small 
size. In the original description (loc. cit.) the length of the last five lower 
teeth (pit-m-j) is given as 52 mm. and the depth of the jaw below mi as 
37 mm., dimensions which in a small individual of A. ovinum are 74 
and 46 mm. respectively. The skull-characters which Ameghino cites in 
his last paper (’07, 74, 76, fig. 12) are not trustworthy, because the speci- 
men figured is a very young animal and agrees closely with young skulls 
of A. ovinum. None of these small skulls has yet been found having 
any indications of horns and it may well be that this was a hornless 
species in both sexes. 
Localities. — The type of A. nitidum was found in the cliffs of the Rio 
Santa Cruz and that of A. corriguenense at Corriguen Aike on the 
Atlantic coast. 
Adinotherium robustum Ameghino. 
Adinotherium robustum Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, 
p- 376. 
Among the material now accessible to me, this probably valid species 
is represented by a photograph of the type in the Ameghino collection, a 
skull (No. 9532) and an incomplete fore-foot (No. 9184), both belonging 
to the American Museum. The skull, which is in a good state of preser- 
vation, though much cracked and somewhat distorted by vertical down- 
crushing, agrees well with the type in size and proportions (cf. Amegh., 
’07, 83, fig. 16), but has quite a different fronto-nasal suture, which is 
more regularly curved than in the type and the nasals narrow less toward 
the posterior end. The skull in question is without frontal boss and is 
therefore probably a female. 
A. robustum is distinguished by its larger size and heavier and more 
robust proportions than in any of the other known species of the genus ; the 
cranium is unusually broad and capacious and the zygomatic arches are 
greatly expanded, even in the female skull. The auditory chamber in 
the post-tympanic portion of the squamosal is inflated so as to form a pro- 
tuberance on the occipital surface, which is more conspicuous than in any 
