524 PHILOSOPHICAL TRANSACTIONS. [ANNO 1799. 



in a moist state; for, without one of these suppositions it is impossible to reconcile 

 such a very great difference. By these experiments of Mr. Hatchett, phosphate of 

 lime was ascertained to be present in the synovia; which though in a very small 

 quantity in the natural state of that fluid, explains the mode by which the crust of 

 enamel on the head of the thigh bone could be produced, when by a morbid action 

 of the parts, the quantity of phosphate was preternaturally increased. 



A mixture of bony matter with the enamel and the substance of the tooth is 

 a structure, as has been mentioned, not confined to the elephant: it is common to 

 all truly graminivorous quadrupeds. But the whole number of grinding teeth 

 belonging to each side of the jaw being confined in a case of bone, so as to form 

 1 large grinding surface, and the teeth being pushed forward from behind, instead 

 of a 2d set being formed immediately under the fangs of the first, as in other 

 animals, are peculiarities not met with in any teeth hitherto described, except those 

 of the elephant. 



These peculiarities have however been ascertained, in the course of the present 

 inquiry, to belong to the Sus ^Ethiopicus ; a skull of which, with the teeth, is pre- 

 served in Mr. Hunter's collection. The particular species to which it belonged was 

 determined, by its exact similarity to a skull, without the grinding teeth, in the 

 British Museum, marked, in Dr. Solander's hand-writing, Sus JEthiopicus, from 

 Guinea. As it has been ascertained by Dr. Solander to come from Guinea, there 

 is reason to hope so curious a species of the hog will attract the notice of natu- 

 ralists, and be the means of perfect specimens being introduced into this country. 

 From the appearance of the teeth in the perfect skull, the animal had probably 

 arrived at its full growth, and only 1 grinder remained on each side of the jaw, 

 consisting of 7 different processes, cased with bone, similar to those of the ele- 

 phant. The grinding surface of those processes which had their points worn down 

 sufficiently to show a transverse section, exposed 3 oval portions of tooth, sur- 

 rounded by enamel, inclosed in bone; which is more like the tooth of the African 

 elephant than the Asiatic, and makes another variety of form of these processes. 



The tusks of the Sus iEthiopicus are uncommonly large, and in their structure 

 resemble those of the elephant. The skull was shown to Sir Jos. Banks, whose 

 readiness to forward the labours of those who engage in the pursuits of science, by 

 liberally communicating to them his own knowledge of the subjects connected with 

 their inquiries, is sufficiently known to the members of the r. s. He identified 

 the species of the genus to which the skull belonged, in the manner above- 

 mentioned; and, by an accurate search among the skulls of animals deposited in 

 the British Museum, discovered a small head in a dried state, which, when pro- 

 perly macerated and cleaned, proved to be that of a young Sus ^Ethiopicus, whose 

 teeth were in a growing state, and enable me to explain all the necessary circum- 

 stances, respecting this curious mode of dentition. The grinding teeth in this 

 young head are distinct from each other, and 4 in number, on each side of the jaw. 

 That which is most anterior is the smallest, and has a grinding surface only equal 



