A MKMOIK UroN THE GENUS 
... .. K.ftiM- referred this tooth to the last upi^er molar 
; w . .e ...... 
. t\Lm- molur, and certainly ha.s not the characters of LnnnoAjo^s 
Suf>rrior /)rniition.-'\'ho nppor molars form a complete senes. The mcisors 
.^nan witl.in outwanl like those of P. palndostis. Marsh says the canine is 
In this respect it agrees in fonn with the canine 
In Marsh’s type specimen tlie external lolx^s of 
iinTeais’ 
larv** and l»n«idly oval at its hast*, 
of I lie larjivr sjH*<des of Palceosyops. 
of the lariier s|H-<-ies ol / i 
,l„. n.,I.Ti..r .m- l.aaiy .lun.agcl. Those of the lx,stenor have their 
.•n.« ii« law with .veil ■i.i.rk.vl internal ha.sal cingnia, which are inoxnnplote. In the 
halt nn-.»..l,.r the |n,n.<v.ne is n.i.eh larger than the n.etaeone ; this is a ehnnieter 
of the toilli niiite .lillennl 1.111 that of. pahidostis, where the e.xtcriial l.ilies of 
till, last im-molar aiv generally eipial. A conspicuous vertical told is present upon 
the panu-one of the last sniH-rior piviiiolar. The last superior premolar of 
/.. latucps is distinguished fmm that of P. pahidostis by the pre.st*nce of a 
w .-ll marked protiH-onnle. 'J’he pivsence of an intermediate conule upon the jire- 
iiioliir m-ries in any sjHH-ies of this subfamily is a very^ rare occurrence, and is seen 
ill only one other s|H*<‘ies. viz: I\i/ccosyops borealis. In P. laticcps the transverse 
diiiiiieter of the hist prcMiiolar is nearly ecpial to that of the first molar. All the 
true molars have low crowns and shallow median valleys; and the transvei*se axes 
of the molars is gnmter than their an tern- posterior axes. The external V’s have 
the same general eharaelei*s as the molars of /^. pahidostis. The external faces of 
all the true niohirs are without eingnla. and the internal cingula of the nu)lai *8 are 
not IIS strongly develo|HMl as in /'. pahidostis. The protocouule and metaeonule of 
iiioliirs 1 ami 2 are iimismilly large, and in the occurrence of the la.st named inter- 
iiusliiite it dilVers from the molar of P. pahidostis, in which a metaeonule is absent. 
< til the lust true molar there is a well marked protocouule. The transverse ridges 
eoiiiiivtiiig the iiitermil eone.s w itii the external lobes are plainly marked, hut they 
an* very low and only sliglitly eon.stricted oil’ from the .surface of the enamel. In 
tin* first and s«*coml iip[H'r molars the transverse ridges arc more developed than 
in the lust sn|H*rior molar. The internal cones of the first two molars are like those 
of /'. fHdudostis U*iiig ^•.|mll ill size, hut in tlie last upper molar the hyptx'one in L. 
Uttiteps x* niuch smaller than the protoeone. As already mentioned under the 
ileM-nption of /*. /HthidosHs, certain varieties occur in that species, charaeterized by 
the pn*s,*i.n. of a ru.limeutary hyi>,H*one upon the last upper molar; this is due to 
the fnet that at the jsistenor internal angle of the molar the cingulum is rai.sed 
vertieiilly almve the surface of the tooth and forms a rudimentary cone. In 
so,..en...s a nidimentary hyiKieone, or perhaps it may be a metaeomde, is devel- 
I I he first .Mtagc* ol the development of the hypocone is the separating 
of the cingnlmn from the laisterior intermediate ecmule ; its further clevelop- 
•' 
