THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
463 
nnd especially wider. A strong cingulum surrounds the crown, which is particularly 
prominent on the inner side and at one point broadens to form an incipient deute- 
rocone. The fourth premolar is shorter and wider than tlie third and is made up, 
as in the selenodonts generally, of two transversely placed crescents; a prominent 
cingulum encloses the crown on three sides, being absent from the external lace. 
The molars increase regularly in size from ml to ml; the former is protruded 
early and always shows more extreme abrasion than any other of the iiermanent 
teeth. The pattern of these molars is too well known to reipiire any description, 
and differs in no point of importance from that found in the European species. 
There is a certain amount of variation in the development of the cingulum ; in 
some specimens it is strongly marked on all sides of the crown except the internal, 
while in others it is interrupted upon the lingual laces of the two internal crescents 
{proto- and hypocones). 
B. Lower Jaw . — The incisors have broad hastate crowns ; the second is con- 
siderably the largest of the series, and the third the smallest. The canine follows 
the incisors without any diastema longer than the spaces which separate those teeth; 
its crown is shaped like the incisors and is smaller than the second of the series. 
The preniolars are of compressed conical shape, and of quite simple construction, 
except in the case of pj. In none of the specimens is the crown of pq preserved, 
but the alveolus shows it to have been smaller than in A. Aymardi, and that it was 
supported upon a single fang. This tooth stands isolated; the space which separates 
it from the canine is slightly longer than that which divides it from p)2- I he latter 
is relatively small and is compressed, with sharp front and hind borders ; faintly 
marked anterior and pjosterior fos.sa' are visible on the inner side of the crown and a 
postero-external one also, bnt there is no cingulum. This tooth is inserted by two 
roots, and in some specimens from the upper beds it is distinctly separated irom piii, 
though not in others ; it suffers much less from abrasion than the other premolars 
of the mandible. The third premolar is much larger than the second, particularly 
in the antero-piosterior direction; it is like the latter in shape, but the inner foss® 
re better marked and an incipient deuteroconid makes its appiearance. The fourth 
remolar is the largest and much the most complicated of the series; deiitero- and 
.aracoiiids are distinctly developed .and enclose a deep valley, ion.img an opiai 
rescciit with the protocoiiid ; the posterior fossa- arc both enclosecl, the miter o 
by the cingohim and the iiiaer one by a ridge descending from tlie _ 
FUbol's figures show this tooth to be of considerably simpler eonstmet.on 
Xl'mis reipuire no p,articular description. As in the 
crown is composed of four h.comp«e ^ Inf m tvt [^di’lnd 
STs V ^ 
ferent species and even m individuals. 
pr 
piarac 
