74 
BUNOTBERIA. 
late molar of tlie Lypotlietical Bunotherium as the starting-point of all more 
specialized forms of crested teeth. The second 'and third lower molars of 
the Peccaries (Dicoiyies) represent snch a t3'pe. It was also pointed out 
that additional tubercles may be added to this, or to a still simpler form, by 
the development of basal cingula. 
Subsequently^ I gave the following account of the homologies of the 
cusps of the sectorial tooth of the inferior series. 
The genus Ilyopsodus presents a modilied form of quadrituberculate 
molar; in the genera Pantolestes and Sarcolemur, Ave observe that the tuber¬ 
cles are similar excepting that the anterior inner is double, or slightly 
bifid. In some of the molars of Tomitherium the tAvo apices of this 
tubercle are separated more Avidely from each other, so as to constitute tAAm 
cusps. These are connected Avith the anterior outer cusp by acute ridges, 
Avhich thus form two sides of a triangular area; Ihe anterior ridge is 
eAudently a developed cingulum. 
The tubercular molar of some Viverridce, and among the Eocene forms 
especially of the Dkhjmictis protenus^ Cope, present a similar structure to that 
just described. This furnishes a ready explanation of the tooth immediately 
in adA^ance, Avhich is the primitiA’e form of the sectorial tooth characteristic of 
that type of Creodonta. The three anterior tubercles are largely developed, 
standing at opposite angles of a triangular space; the outer and anterior 
cusps are the most eloA^ated, and the ridge Avhich connects them is noAv a 
cutting blade. The posterior portion of the tooth does not share in this 
eleA^ation, and its two tubercles are in some genera obsolete, and in others 
replaced by an eleAaation of one margin, which leans obliquely toAvard the 
middle of the croAvn. In Mesonyx^ this is represented by a median longitu¬ 
dinal crest. If the tAvo tubercles of the posterior part of this tooth (AAdiich 
I have termed a tiibercidar sectorial) are elevated and acute, Ave liaA’e the 
molar of many recent and extinct Insectivora; if the same portion, now 
called a heel., is much reduced, we have the type of Oxycena and Stypoloplius. 
In the Canidce^ the three anterior tubercles are much less eleA-ated than in 
the genera above named; the external is much the larger, and the anterior 
remoA^ed farther foi’Avard, so as to giA^e the blade a greater antero-posterior 
* Pioceediiigs of the Academy of Philadelphia, 1875, p. 21. 
