198 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
In all of the many skulls belonging to the latter species which I 
have examined, the triangular forehead is quite smooth, but in N. 
cornutus there is a low median protuberance, or boss, in the posterior 
portion of the forehead between the converging supraciliary ridges, very 
much as in Adinotherium. Very probably, this protuberance indicates the 
Fig. 37. 
Nesodon imbricatus: Occiput, X b (No. 15,437.) 
presence, in the living animal, of an incipient dermal horn. Behind and 
on each side of the protuberance the forehead is finely rugose and quite 
different from the smooth surface seen in the other species. Above the 
orbits, the frontals have an unusually swollen appearance, due, no doubt, 
to a large development of the sinuses, and the postorbital processes are 
longer and more pointed than in the preceding species. The fronto-nasal 
suture resembles that of Adinotherium in form and in the absence 
of nasal processes of the frontals, but no dependence can be placed upon 
this character without a very large suite of specimens. From a single 
individual it is not possible to say whether this suture is constant or fluc- 
tuating. 
