EVIDENCES FROM PALAEONTOLOGY 79 
which is believed to indicate the existence of a short proboscis 
extending at least to the tips of the tusks. 
Trilophodon.— Trilophodon, a great migrant and consequently 
wide-spread over several continents as stated above, exhibited in 
several respects a striking advance over Palaeomastodon;, but this 
advance was in the main in the same direction as was indicated by 
the change from Moeritherium to Palaeomastodon. Trilophodon was a 
huge animal, nearly as large as modern Indian elephants. The tusks 
were considerably longer (Fig. 5, D’) and still bore a band of enamel. 
The molar teeth were large and greatly reduced in number, so 
that only two were present at any one time on each side of each 
jaw. The surface of these teeth bore a somewhat larger number of 
transverse crests (Fig. 5, D) than were present in the earlier forms. 
The lower jaw was enormously elongated, so that it projected as far 
forward as the tusks. The great weight of the lower jaw and tusks 
was associated with a considerable development of cancellate bone 
in the skull, to which the supporting muscles of the neck were 
attached. Presumably there was a proboscis which extended to or 
beyond the tips of the tusks and lower jaw. 
Mastodon.—The mastodons on the whole represent a line of 
development which became extinct; but in their incipient stages they 
appear to have given rise to the succeeding forms leading to the 
elephants. The body was somewhat larger than that of Trilophodon, 
being about the size of the Indian elephant. The tusks (C’) were 
much elongated (9 feet or more), but the lower jaw was greatly short- 
ened and the lower incisor teeth were reduced or wanting. The molar 
teeth (Fig. 5, C) were scarcely more complex than earlier forms, and 
numbered two on each side of each jaw. They were still crushing 
teeth, and the food must have been tender twigs and succulent plants; 
indeed, remains of such objects have been found in the region of the 
stomach of the fossil mastodons. 
Stegodon.—This animal is of interest chiefly because the molar 
teeth bore five or six well-defined transverse ridges (Fig. 5, B). These 
ridges were due to plates of enamel extending up through the tooth, 
and inclosing a substance known as dentine. Over the enamel in an 
unworn tooth was a thin coat of a third substance called cement, but 
there was not much of this substance between the ridges. In the 
latter respect Stegodon differed, as is pointed out below, from the 
elephants and mammoths. On the whole, Stegodon was intermediate 
between the mastodons and elephants. 
