3i8 THROUGH THE HEART OF PATAGONIA 



dome ; while its antero-superior angle is not rounded as in Mylodon, but 

 •curves upwards and forwards and ends in a point as in Grypotherium. At 

 the oral border there are the shattered bases of four teeth. 



A fragment of the nasal region (No. 13) may also have belonged 

 "to the same skull, but its state of preservation is a little different from that 

 of the two specimens just described. It has clearly been buried in a 

 powdery deposit, which has stained it brown ; but the enveloping dust 

 must have been extremely dry, for fragments of cartilage adhere to it, 

 -as well preserved as in the nasal chamber of the cranium itself (No. i). 

 It also bears traces of the integument. 



Judging by the figures of the skull of Grypotherium published by 

 Reinhardt {loc. cit.), this specimen seems to have occupied an anterior 

 position in the nasal region. It is thus of great interest, because the 

 three known skulls of Grypotheriu7n leave the precise nature of the 

 bony arcade separating the narial openings undecided. According 

 to Reinhardt, the nasal bones terminate as in Mylodon, and the arcade 

 is an element interposed between them and the premaxillas. Accord- 

 ing to Burmeister, the nasals themselves extend forwards and consti- 

 tute the greater part, if not the whole, of the problematical bar. The 

 fragment now under consideration is clearly in favour of the latter inter- 

 pretation. Its lower thickened end is a massive bone, not bilaterally 

 symmetrical, and not showing any trace of a median suture. Its inferior 

 face is irregular and roughened, and can scarcely be regarded as an 

 articular facette. Its upper portion consists of a pair of bones sepa- 

 rated by a very well-marked median longitudinal suture. These are 

 not thickened at their contracted upper end, where they have evidently 

 been broken, and are not quite bilaterally symmetrical. They doubtless 

 fuse at their lower end with the problematical azygous bone already 

 mentioned, but the arrangement is obscured by the enveloping soft parts. 

 A pair of bones, which may be regarded as nasals, thus extend forwards 

 in a narrow arch to a point just above the anterior end of the premaxillse ; 

 while the massive bone effecting a union between the two normal pairs 

 of elements is probably an ossification in the internasal septum. It is 

 interesting to note that there is an incipient trace of a similar forward 

 production of the nasals in the genus Scclidotherium ; while there is 

 sometimes an ossification of the internasal septum in Megatherium.*' 



The three specimens now described, when placed approximately in 

 their natural positions, afford a very satisfactory idea of the form and 

 proportions of the skull when complete. The malar bone is the only 

 important part to be added ; but unfortunately it is impossible to decide 

 which of the three specimens of this element in the collection belongs to 



- R. Lydekker, Anales Mus. La Plata— Paleont. Argentina, vol. iii. pt. a (1894), 

 p. 73, pi. xlv. Fig. I. 



