BUNOTHERIA. 
73 
cusp as well. An inspection of the molar teeth of the ilfamwmZm generally, 
confirms the view taken by Professor Allen, i. e., that the posterior inner 
cusp is appendicular to the anterior or true representative of the inner root. 
The way being- thus prepared, it is a comparatively easy matter to 
trace the homologies of the cusps of the superior sectorial tot)th of the Car¬ 
nivora. In Procyoii, the posterior inner tubercle is smaller than the anterior; 
the same is true in the insectivorous genus JErinaceus. In Ursiis americanus, 
the posterior inner tubercle is the larger, if its position and the occasional 
presence of a rudimental cusp in front of it truly indicate its homology. In 
Scalops, the posterior inner tubercle is wanting. In Carnivora generally, it 
is wanting; and the anterior tubercle has a much smaller development than 
the external ones, being largest in the Yiverridco. 
The flattening of the external tubercles has resulted in the ungulate 
series, in the crescentoid patterns of the Perissodactyla and Artiodactyla. The 
same process, slightly modified, has produced the sectorial blade of the su¬ 
perior dentition of the Carnivora. The essential difference in the two cases 
is, that in the former the resulting crests are concave, not separated by a 
fissure, and readily worn at the summit, by which they soon lose the cutting 
character; in the latter, the crests are in a single straight line, are separated 
by a fissure, and are furnished with a deep layer of enamel on the superior 
edge. The crests are also, in the Carnivora, always unequal. 
This inequality is due to the greater elevation of the anterior crest, or, 
as it should be termed in the greater number of genera, anterior cusp. This 
cusp is homologous with the principal cusp of the other premolars, while the 
posterior crest of the sectorial is represented in the Canidm and Felidco by the 
combined posterior lobe and heel of the typical premolars. In some other 
groups, the posterior blade may represent the heel only of the premolars; 
and, in Prototomus and Oxycena from the American and Pterodon (teste Ger- 
vais) from the European Eocene, there are two cones in place of the anterior 
cusp of the sectorial, the posterior of which may represent the posterior 
cutting lobe of the premolars of the Canidce, &c.; but this is not absolutely 
certain. 
In a former essay,* I regarded the simple four-lobed or quadritubercu- 
*Ou tbe Homologies and Origin of the Types of Molar Teeth of Mamm. Educabilia, 
Phila,, 1874. 
