354 Zoological Society. 



produced ; the third trapezoid, obUquely 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. 



SCELIDOTHERTUM, Oweu. 



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

 racter of its frontal process cannot be determined 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. 



Platyonyx, Lund. 



This genus is proposed by Dr. Lund, to include a series of species 

 discovered by him, the first three of which he had previously referred 

 to the genus Megalonyx, and Prof. Owen, in the conspectus at the 

 end of his memoir on the Mylodon, has placed them in his genus 

 Scelidothermm ; but I prefer to adopt, for the present. Dr. Lund's 

 latest arrangement, since in the lower jaws figured, the last lower 

 molar has a deep groove on its posterior side, and the fourth species, 

 of which an entire skull is figured (tab. 38), agrees in this cha- 

 racter, and shows a marked distinction from the S. leptocephalum in 

 the zygomatic arch being incomplete ; the malar bone has no frontal 

 process, and but a shght angular indication of the zygomatic process. 

 P. Cuvieri. P. minutus. 



P. Bueklandi. P. Brongniartii. 



In addition to these. Dr. Lund represents a metacarpal bone of a 

 species which he calls P. Owenii, and an os scaphoides of the foot of 

 another, which he names P. Agassizii. 



The genera Coelodon and Sphenodon of Dr. Lund seem open to 

 the objection suggested by Prof. Owen, namely that the teeth would 

 be first developed in the form of hollow obtuse cones, not assuming 

 the cylindrical form until worn down to the part which has acquired 



