PROFESSOR OWEN ON SOME SPECIES OF THE EXTINCT GENUS NESODON. 301 
fold, a, is obliterated except at its end, which forms the enamel-island b, fig. 10 , and 
the deep termination of the second fold forms the second island, c, which is separated 
from the rest of the fold, which also forms an island, d. 
In the next molar, the deep beginning of the second fold, d, still communicates with 
the enamel covering the inner side of the molar: the two branches of the forked 
fold, a, retain the continuity with the main stem, and the only island is that (c) formed 
by the sunken end of the second fold. On the implanted side of the crown of the 
first molar the obtuse blind ends of both folds project into the bottom of the pulp- 
cavity of the crown, from which the beginnings of short roots are seen to diverge. 
The bases of the two folds are seen to be more distinct in the wider pulp-cavity of 
the second and less worn tooth. The crowns of both teeth have had the same curved 
form as in the Nesodon ovlnus ; but the greater part has been worn away. 
Part of the Lower Jaw and some Teeth of the Nesodon imbricatus. 
The fossil which originally indicated the genus, and was referred to the species 
imhricatus*^ consists of the symphysis and part of the right ramus of the lower jaw 
(Plate XVII. figs. 11 , 12 , 13 , 14 ). The symphysis is obliterated by complete confluence 
of the rami at that part ; it is rounded anteriorly and slopes downwards and back- 
wards at an angle of 120 ° with the lower border of the rami ; these are slightly 
concave along the outer walls of the sockets of the anterior premolars, as if the 
rami had been gently pressed together at that part, in advance of which the symphysis 
slightly expands before forming the convex termination supporting the incisors. 
These teeth (i i, 2, 3, figs. 11 , 12 , 14 ) incline forwards at the same angle as the sym- 
physis, and increase in size from the first to the third ; the summits of the crowns 
have been worn to an almost flat elongated oval or crescentic surface, from I2 to 
2 lines in the smaller diameter. Those of the first pair (i 1) are in contact, the con- 
tracting bases slightly diverging to their insertion, which is by a long and slender 
fang; the length of the enamelled crown is 8 lines, the breadth at the worn summit 
4 ^ lines ; this is thickest at the inner border, when the thickness so increases towards 
the fang as to give a three-sided figure to the transverse section of the base of the 
crown: the length of the fang is 1 inch, fig. 12 . 
The second incisor (i 2) is situated partly behind and to the outer side of the first, 
so that the mesial angle of the crown is overlapped anteriorly by the outer angle of 
that of the first incisor. The crown of the second has its anterior surface almost 
equally divided into two facets, which meet at an angle which marks the extent of the 
overlapped part of the crown. The posterior surface of the crown is divided un- 
equally, the intervening angle or longitudinal eminence being near the inner rounded 
border of the crown. This is 9 lines in length, and nearly 6 lines in breadth at the 
worn surface. The fang contracts as it descends in the socket, and is 1 inch 1 line 
in length, fig. 12 . 
* Loc. cit. p. 66. 
2 R 2 
