126 
FOSSIL JAWS OF MACROPODID^, 
by a raised tubercular basal rim enclosing a concave ledge. Outer 
surface of crown impressed at anterior third, the impression 
defining the outer edge of an anterior cusp b; on the posterior 
half of the impression are two very distinct vertical ribs. In a 
maxilla which seems to belong to this species -the premolar (PI. 
xviii. fig. 8) is elongate obovate, with diameters 12*3 and 5-7 and 
a little contracted at the anterior third. The intero-posterior 
tubercle is more entirely separated from the lobe; and the whole 
tooth has a facies different from that of the preceding tooth, which 
may be taken as the type of the species. Yet as m. 1 in this 
maxilla has relics of the sepiment in its outer midvalley, and as 
the variation in the premolar may be paralleled among recent 
species, there is not at present sufficient ground for referring it to 
a separate species. 
Molars (PL xviii. fig. 10). — The posterior molars differ in no 
respect from those of M. magister save in somewhat superior size; 
m. 2 most frequently shows a vertical fold descending from the 
middle of the hinder surface of the fore lobe external to the mid- 
link, and meeting its fellow of the opposite side at the bottom of 
the valley b; or as in the type specimen forming there an erect 
plate. In m. 1 this fold forms a more complete sepiment a from 
lobe to lobe; it is constant in occurrence, and traces of it are 
visible as long as the lobes persist. It is not a little remarkable 
that this one of the structural characters of Palorchestes should 
reappear in a species of Macropus. 
Mandibular. — P. 4 (PL xviii. fig. 7) ovate, with the sides mesially 
contracted, and with diameters 8*0 and 4-0. Crest mesial; a very 
small intero-posterior cusp separated from the lobe apically and 
posteriorly; inner side of crown somewhat concave in front of the 
cusp, outer rather concave with one or two obscure 'ribs about the 
middle. The cusp disappears under wear. A series of four young- 
teeth extracted from their crypts at an early stage of growth or 
exposed from above shows that the tooth in its growth undergoes 
considerable change of form. At the earliest phase observed it 
resembles in shape the end of a cold chisel with a dent on each 
