154 



to point out some peculiarities in the structure of the cranium which indicate 

 the chief instrument by which the foliage was stripped from the prostrate tree 

 and introduced into the mouth. 



These indications are the deep and well-defined cavity in the mastoid bone 

 for an unusually strong and secure articulation with the os hyoides, and the 

 great capacity of the anterior condyloid foramina which give issue to the motor 

 nerves of the tongue ; they combine with the ascertained size and structure of 

 the bones of the tongue in affording unequivocal evidence of a very remarkable 

 development of the muscular part of that organ. 



The above-mentioned nervous foramina in the Giraffe, which, besides being 

 the largest species of its order, is that which makes most use of its tongue in ob- 

 taining its food, are but half the size of those in the Mylodon ; and, indeed, 

 when these capacious outlets first attracted my attention in a separate fragment 

 of the cranium of a cognate species, without any other part of the skeleton to throw 

 light on its habits and food, I had no other analogy to guide me in forming an 

 idea of the use of the much-developed muscular organ indicated by them than 

 that of the Ant-eaters*. We may now, however, readily imagine a great Sloth- 

 like quadruped, daily exercising its tongue in rending off" the twigs and smaller 

 branches of trees, to have required an organ as large and strong as the anterior 

 condyloid foramina prove it to have been. If the foregoing evidence had been 

 absent, the great breadth of the smooth concave surface of the symphysis of the 

 lower jaw in the Mylodon would have indicated the bulk of the prehensile tongue 

 which, in the living animal, ghded to and fro upon it : no incisor teeth inter- 



* See the description of the Glossotherium in the ' Fossil Mammalia of the Voyage of the Beagle,' 

 p. 57, pi. x\n. The reference of the cranial fragment of the extinct animal so-named to the Edentate 

 order, and the inference from the indications of the temporal muscle that it possessed teeth (p. 59), are 

 confirmed by the subsequent discovery of the entire cranium of the Mylodon robustus ; the question 

 (p. 63) whether the fragment might not belong to one or other of the extinct Edentata, the lower jaws 

 of which are described in the same work, is ailSrmed in favour of the Mylodon. Specific difi"erences 

 may be detected between the fossil in question and the corresponding part of the skull of the Mylo- 

 don robustus, and it is, therefore, highly probable that it belongs to the Mylodon Darninil, with 

 which the term Glossotherium may now be regarded as synonymous. The error in my conjecture as 

 to the nature of the food of the Glossotherium, into which I was led by the analogy of the Myr- 

 mecophaga, is corrected by the discovery of the remains of Edentata in which the predominant use of 

 the tongue in obtaining food from the vegetable kingdom appears to have been second only to that in 

 the Ant-eaters. 



