MEGATHEEIID^. 99 



18621. The left tibia. This bone is longer than the tibia of /S'. lep- 

 tocejyJialum (No. 37472), and differs by the form of the 

 distal articular surface, the f acette for the external trochlea 

 of the astragalus being in a higher plane than that for the 

 internal tuberosity, and the facette for the latter relatively 

 smaller; the facette adjacent to the fibula is smaller and 

 placed at an obtuse angle to the other two facettes, instead 

 of being nearly in the same plane. There is a foramen on 

 the internal border below the head, which is wanting in 

 S. leptocejohalum. 



18744. The right tibia. The facettes for the astragalus are slightly 

 different from those of the preceding specimen, but the other 

 characters are similar. 



18620 k. The left astragalus, belonging to the same individual as the 

 (Figf.) tibia, No. 18621 . This bone, which has lost the extremity 

 of the internal tibial tuberosity, is described and figured 

 by the present writer, oj:). cit. p. 495, pi. xlix. fig. 4 ; it 

 _ differs from the type astragalus of S. leptoceplialum by the 

 great projection of the external trochlear ridge above the 

 level of the internal tuberosity, and is thereby intermediate 

 in character between that bone and the astragalus of 

 Megatlierium, although wanting the navicular cup of the 

 latter. It agrees precisely with the corresponding bone of 

 the foot figured by Burmeister in the ' Monatsb. k. preuss. 

 Ak. Wiss.' 1881, plate facing p. 380, fig. 2, under the 

 name of -S'. leptoceplialum. 



18935. The conjoint first and second phalangeals of the third digit 

 of the pes. This bone differs from the corresponding pha- 

 langeal of /S. leptoceplialum (No. 37492) by the absence of 

 the backward projection of one side of the superior sur- 

 face. 



18620 X. The conjoint first and second phalangeals of the third digit 

 of the pes, imperfect on the palmar aspect. 



Scelidotherium chiliense, Lydekker\ 



This species is characterized by the extreme breadth and short- 

 ness of the nasals and maxillae, and the want of production of the 

 anterior part of the mandible. The length of the nasals does not 



' Pro.\ Zool. Soc. 1880, p. 490. 



n2 



