58 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



sideration ; for the glenoid cavity is so shaped as to allow the lower jaw free motion 

 in a horizontal plane, from right to left, and forwards or backwards, like the move- 

 ments of a mill-stone; and, nevertheless, I venture to affirm it to be most probable, 

 that the food of Glossotherium was derived from the animal and not from the vege- 

 table kingdom ; and to predict, that when the bones of the extremities shall be 

 discovered, they will prove the Glossothere to be not an ungulate but an unguicu- 

 late quadruped, with a fore-foot endowed with the movements of pronation and 

 supination, and armed with claws, adapted to make a breach in the strong walls 

 of the habitations of those insect-societies, upon which there is good evidence in 

 other parts of the present cranial fragment, that the animal, though as large as an 



ox, was adapted to prey. 



We perceive, in the first place, looking upon the base of this portion of skull, 



a remarkable cavity, situated immediately behind the tympanic bone, of nearly a 

 regular hemispherical form, an inch in diameter (fig. 2, b, PL XVI). The super- 

 ficies of this cavity appears not to have been covered with articular cartilage, for 

 it is irregularly pitted with many deep impressions ; and I conclude, therefore, 

 that it served to afford a ligamentous attachment to the styloid element of a large 

 os hyoides. With this indication of the size of the skeleton of the tongue, is com- 

 bined a more certain proof of the extent of its soft, and especially its muscular 

 parts, in the magnitude of the foramen, for the passage of the lingual or motor 

 nerve (c. fig. 2 and 3). This foramen, (the anterior condyloid,) in the present spe- 

 cimen, is the largest of those which perforate the walls of the cranium, with the 

 exception of the foramen magnum ; it is fully twice the size of that which gives 

 passage to the second division of the fifth nerve ; its area is oval, and eight lines 

 in the long diameter, so that it readily admits the passage of the little finger. 



It is only in the Ant-eaters and Pangolins that we find an approximation 

 to these proportions of the foramen for the passage of the muscular nerve of the 

 tongue ; and the existing Myrmecophagous species even fall short of the larger 

 fossil in this respect. Some idea of the size of the lingual nerve, and of the organ 

 it was destined to put in motion, may be formed, when it is stated that the foramen 

 giving passage to the corresponding nerve in the Giraffe, — the largest of the Ru- 

 minants, and having the longest and most muscular tongue in that order, — is 

 scarcely more than one-fourth the size. 



With these indications of the extraordinary development of the tongue, we are 

 naturally led, in order to carry out a closer and more detailed comparison of the 

 fossil in question, to that group of mammalia in which the tongue plays the chief 

 part in the acquisition of the food. The size, form, and position of the occipital 

 condyle, — the magnitude of the occipital foramen, (which must here have some- 

 what exceeded three inches in the transverse diameter,)— the slope of the occipital 

 surface of the cranium from below, upwards and forwards, at an angle of 60° 





