1879. | Geology and Paleontology. 59I 
The skull is that of an old animal, as the sutures are almost 
entirely obliterated. Its length is .610 m. (a little more than two 
feet), which would make the creature, when alive, intermediate in 
size between Megatherium americanum and Mylodon robustus, and 
therefore belonged to one of the largest forms of the family yet 
discovered. The most remarkable feature of the cranium, and 
one which is without a parallel in the family, and hence at once 
distinguishing it from all allied forms, is the singular structure of 
the muzzle. The intermaxillary bones are completely coossified 
(owing, perhaps, partly to the age of the animal), and rise verti- 
cally upon the median line in the form of a buttressed bony arc 
to unite above with the anterior extremity of the nasal bones, 
parts in Rhinoceros tichorinus, and in the absence of an osseous 
nasal septum, more notably that of R. merckit, in which the bony 
nasal partition is oy partially ossified. There is abundant 
evidence to show that this arch is not a part of the nasals pro- 
longed forward, since there is a suture separating the latter from 
the intermaxillaries proper. The structure, however, in this 
erat of— 
a. Aphelorhine ; with unspecialized intermaxillaries. 
b. Diarhine; with intermaxillaries vertically produced and 
joined by suture to the anterior meer! of the nasals, and 
dividing the external nares as in Grypotherium. 
The intermaxillary arch dividing he external nares, but with- 
Out an osseous nareal septum, recalls the arrangement of the 
bones of the muzzle of certain lizards, more particularly those of 
_ Lguana, 
The tooth formulz of some of the extinct genera may be com- 
pared as follows: 
5—5 
Scelidotherium and Mylodon E a ues tas molars pence 
: 4—4 
nd ee a 
Grypotherium . ay 4—4 
4—4 
Celodon On oc ireerseter 
