PETERSON: A REVISION Or, THE ENTELODONTIDAl 83 
transverse development of the tubercles. The fissure which corresponds to that de- 
scribed on the anterior face of My is present on M; but is entirely closed in by the 
lateral horns of the proto- and metaconids. ‘There are slight cingula on the antero- 
external angles and the external face of the hypoconid is surrounded by a heavy 
mammillated cingulum. Posteriorly there is a heavy basal ledge and a minute 
hypoconulid which is located at the base (posteriorly), between the hypo- and ento- 
conids. One of the more significant characters of the lower dentition is seen in the 
relatively greater development of the hypo- and entoconids, which causes the nar- 
rowing of the cross-valley between the latter and the anterior tubercles. 
There were found in quarry No. 1, the third lower molars of the right and the 
left rami (Vert. Foss., 1835 ; 2114), which differ from Mg in the type of Dinohyus, 
by having the hypoconulid well developed. The cross-valley between the anterior 
and posterior tubercles is also interrupted externally by a heavy cingulum. The 
postero-external face of these teeth are otherwise quite smooth, while in Dinohyus 
hollandi, there is a continuous cingulum from the cross-valley to the posterior face 
of the hypoconid. These teeth may possibly represent another genus, but are in- 
adequate as types. 
The molars of Mntelodon differ from those of Dinohyus in having the postero- 
internal cusp (entoconid), especially on My and Mz much less developed. ‘The 
ledge produced by the cingulum on the posterior margin of the crown, which is so 
prominent in Dinohyus, is only very slightly represented in Hntelodon. The cingula 
are also better represented on the molars of Hntelodon than in those of the American 
genus. The most important feature of the lower dentition is seen in the greater 
development of the posterior portion of the crown of Mg in Dinohyus than in 
Fntelodon which in the former is distinctly more specialized than in the latter genus. 
This same feature of Mz is also observed on comparing Dinohyus with Archexotherium. 
MEASUREMENTS. 
Mm 
Hue g tly OL AMTOTOT aCeNUlblOten veces se atecsin cc areccenecee- (eee Geert ts cckeyew ecu iain 465 
ce frOMAIMEGIATISIN CIS Olt OM sree ncrepaeePess VeNCa<ocs Corea edunttMGis cece alive 825 
OC sOle TO Olax saelle sera tecsr 1387 
Antero-posterior diameter of I. 16 
Transverse ss 12 
Antero-posterior — “ 25 
Transverse os 19 
Antero-posterior  ‘ 34 
Transverse oS “TT. eS eo oe 27 
Antero-posterior “ ofcanine ‘“ Kb ‘ 48 
oe 73 oe “cc (73 
Transverse 
