MOLAR TEETH AND OTHER REMAINS OF MAMMALIA. 
15 
quently tlie entrance to the valley is remarkahly low^ almost on a level with the 
base of the crown, and below that of the cingulum. ; there is no tubercle at the 
entrance ; the basis of the two coUes are in contact along the bottom of the valley. 
At a distance of one inch from the internal border of the crown the median 
collis gives off a very large and thickened crochet, which is directed forwards and a 
little inwards ; the neck of the crochet is constricted, and there is no process of 
enamel in the angle formed between the. internal wall of the crochet and the anterior 
wall of the median collis | the crochet thickens slightly in the middle, and again con- 
tracts towards its free extremity ; at a level a little below that of the present surface 
of the crown, the crochet extends completely across the median valley ; there is no 
loop of enamel on its external wall | the moiety of the median valley situated on 
the inner side of the crochet forms a triangle with curvilinear boundaries, the 
whole of which is visible from the inner side of the tooth. Externally to the cro- 
chet the valley is trefoil-shaped ; the leaves of the trefoil are divided by two pro- 
cesses,' — firstly, a smaU wedge-shaped combing-plate, projecting into the valley from 
the outer side of the tooth ; and, secondly, a similarly shaped antecrochet from the 
anterior collis. The direction of the combing-plate is exactly at right angles to the 
internal border of the crown of the tooth: when worn down the surface of the 
crown would display four fossettes,' — one formed by the posterior valley ; a second 
consisting of that portion of the median valley which is internal to the crochet. 
This fossette would not be completely isolated until the tooth becomes worn down 
almost to the base of the crown, owing to the low level of the entrance to the 
median vaUey i the two other fossettes would be on the outer side of the crochet, 
divided from each other by the combing-plate ; they would be isolated at an early 
period of wear. 
The dentine- surface of the anterior collis is directed at an angle of 45° to the 
internal border of the crown, so that the outer extremity of the median valley is 
produced towards the antero-external angle of the tooth. 
The anterior side of the tooth {on the right of the figure) has an undulating 
outline, prominent in the centre ; a wavy cingulum runs along the whole length of 
this surface ; on the internal half of this side the cingulum diverges from the main 
wall, and forms a well-marked triangular '' anterior valley,” extending up to the 
antero-internal angle of the anterior collis. There is no trace of any cingulum 
along the internal surface. 
The posterior valley {on the extreme left of the figure) is of very large size, 
and has a regular oval shape ; the longer axis of the oval is nearly parallel with the 
antero-posterior axis of the crown; the external wall of this valley is nearly verti- 
cal, while the internal wall slopes rapidly away towards the median collis ; the pass 
into this valley is sharply defined, forming a ridge descending from the summit of 
the median collis ; the pass leading into the posterior valley is considerable above 
the level of that leading into the anterior valley, and above that of the cingulum, 
so that this valley would be isolated at a very early period of wear. 
( 33 ) 
