PAL.EOSYOPS LEIDY, AND ITS ALLIES. 
3r,:{ 
cones of the last upper molar are lai’ge and etfual in height, there is no such 
transition. For the present, therefore, and until more ahnndant material is dis- 
covered, it will perhaps be better to leave those forms in which the last upi>i*r 
molar has two internal cones in the Limnohyops, with the undei-staiiding that 
this genus should not have a generic value equal to that of Palceosyops. A ca.se 
parallel to the above is that of Titanothermm Leidy and Diconodoti .Mai>h. Prof. 
Osborn' holds that the latter genus cannot be separated from the other, Imcaust* the 
hypocone of the last upper molar is found in all stages of develoj)ment in the difler- 
ent species of these two genera. He found the ])re.sence or absence of the first 
lower premolar in Titanotherium a very vai’iahle character, which is not, however, 
the case in Palceosyops and Linmohyops, where both genera have the same miiulier 
of teeth above aiid below. 
Skull (PI. XI, figs. 8, 9). — The Princeton collection contains a very fine oc'cipital 
portion of a skull of L. laticeps. It was collected in the Bridger basin and is one 
of the best preserved skulls in the museum. The cranium was ivfern*il by Scott 
and Osborn, in their report for 1877, to P. mmor, hut 1 find upon comijaring it witli 
Marsh’s original type of Z. laticeps, that it should be referred to Liuntohyops. 'flu* 
measurements of this cranium are considerably less than those of .Marsli’s ty|H‘. an«l 
it may possibly represent another species, although tlie height of the <K‘ci|»itnl civsfs 
and the width of the same region are very variable characters, and may differ wiilely 
in their dimensions in the same species, as we can readily iirove by exaniiiiing. for 
example, a number of skulls of the genus Urstis. 
General fo7'in (Fig. 2, p. 289). — In general form the skull differs from that of P. 
paludosus or P. megarhhms. Its doi’sal contour is very much like that ()f the |{hin(H'ei-os. 
being slightly- depressed in the frontal region and rising gradually to tin* «M-ci|mt. whiU* 
the latter region is much higher than the anterior portion of the skull. 'I’he (KTipnl 
is provided with a great development of the lambdoidal and sagittal eivsts. which aiv 
much heavier than in any other species of this subfamily. 'I'he nasal n-gion is 
rather elongated and slender and closely resembles that of /'. Icreidats in the form 
of its nasals. The skull as a whole is more elongated and deiuvssial and has a 
shorter facial region than that of P. paludosus. The orbit is rather .small ami 
placed well forward, its anterior termination being over the anterior Imrder of the 
second molar. The floor of the orbit in L. laticeps is short as in P\ paludosus. 
The orbit is separated from the temporal fossa by a well marked jiost-orhital 
process. The temporal fossa is rather low, much elongated and very deeply exca- 
vated, more so in comparison with the size of the skull than in any other s|K‘cies of 
this subfamily. The zygomatic arch is heavy and wide spivading. We may add 
that the projecting processes of the cranium ai-e exceedingly strongdy develo|HMl. 
The occiput is rather low, broad, with wide projecting pann-cipital pnK'es.-M>s. 
iPreliminary account of the Fossil Mammals from the White River Fonnati..n, etc., (wg.- hVs. Hull. 
Mus. of Comp. Zoology, 1887 . 
