210 



the zygoma, the supratemporal process rising obliquely ; pterygoid 

 bones thin and compressed ; crotaphite impression approaching near 

 to the occipital ridge ; tympanic hone reduced and separate ; (the 

 foregoing characters can of course apply only to the Mylodon robustus, 

 it being the only species of which the cranium is known ;) lower jaw 

 broad and more or less prolonged in front, the lower outline straight, 

 the condyle depressed ; teeth ^, the anterior ones rounded or tri- 

 gonal, the posterior ones larger, trigonal in the upper jaw, gradually 

 becoming bilobed in the lower. The species can only be characterized 

 by the lower jaw, as it is the only part that is known in all of them. 

 The characters are taken chiefly from Prof. Owen's works. 



M. Darwinii. 



Lower jaw much produced anteriorly, with a double mammelliform 

 tuberosity upon the symphysis below. The first tooth rounded or 

 subtrigonal, the second subelliptical, with a slight depression on the 

 inner side ; the third subquadrate, grooved on the inner side ; the 

 posterior internal angle produced ; the fourth bilobed, sharply grooved 

 on the inner side. 



M. Harlani. 



Lower jaw with the symphysis short ; the second tooth sub- 

 quadrate, grooved on the inner side, with the posterior internal angle 

 produced ; the third trapezoid, obliquely placed, with the inner side 

 rounded ; the fourth bilobed, the inner groove biangular, and a small 

 shallow one anterior to it. 



M. ROBUSTUS. 



Lower jaw produced and very broad anteriorly, the first tooth 

 round, the second subtrigonal, grooved internally, the third sub- 

 quadrate, oblique, the fourth bilobed, with a deep scallop on the 

 inner side and a smaller one anterior to it. 



Glossotherium, Owen. 



Crotaphite impression approaching near to the occipital ridge ; 

 tympanic bone reduced and separate. The general cranial characters 

 are unknown, but the fragment is recognizable by the great size of 

 the surface for the stylohyal bone, and of the precondyloid foramen. 



SCELIDOTHERIUM, OwCU. 



Malar bone with a well-developed zygomatic process ; the cha- 

 racter of its frontal process cannot be determmed through mutilation 

 of the specimen ; crotaphite impression approaching near to the occi- 

 pital ridge ; tympanic bone reduced and separate ; lower jaw greatly 

 curved below, its condyle depressed ; teeth ^^, transversely extended, 

 the anterior ones fully as large . as the others, the first in each jaw 

 elongate trigonal, the others gradually becoming bilobed, the last 

 upper one trigonal. 



<S. leptocephalum. 



