258 The Creodonta. [March, 
the carnivorous type of this series, the group now under discus 
sion, I have called the Creodonta.! Its definition is as follows: 
Neither incisor nor canine teeth growing from persistent pulps 
Hallux not opposable. Superior true molars tritubercular or 
more simple. 
The only character which distinguishes the suborder from the 
Insectivora is the possession of tritubercular or more simple 
molars above. This is, as I have shown, a feature of more it 
portance than has been hitherto supposed. The trituberculi 
molar is the primitive type from which the quadritubercular 
has been directly derived. It has furnished the starting point fr 
both the carnivorous and the herbivorous dentitions, since it wè 
common to both the clawed and hoofed mammals of the Putt, 
or lowest known epoch of the Eocene period. 4 
So far as known, the Creodonta were all plantigrade, and bi 
long tails, and were mostly five-toed. With the possible excep 
of Protopsalis tigrinus, they all had relatively larger heads a 
shorter legs than the majority of the Carnivora of the pres 
period. This is true of all the recent Creodonta, 
reach the dimensions of many of the fossil forms. e 
The contents of the suborder Creodonta display, in ther mi 
fications, the usual range of simplicity and complexity c0 
with the type, and the families may be arranged in some ; 
phylogenetic order, in accordance with this principle. ™ 
less a difficulty arises as to what are ancestral or primitive 
tions, and what characters, if any, must be regarded as the re 
of degradation. As other parts of the skeleton are less ee | 
obtained, these considerations relate chiefly to the dentition. 4 
In my paper on the Homologies and Origin of pe“ 
Molar Teeth, etc.? I pointed out that the cone was er b 
form of tooth from which all others must have been deni 
the Mammalia this may have been modified in several mot | 
ultaneously, but two methods present themselves as the rene sit 
tain secondary primitive types. The first of these is that 5 
ple premolar, where the cone is compressed, and 1s sooner sil 
followed by a horizontal extension or heel. This type Pi 
phia Academy” 
1 For greater detail on this topic, see Proceedings Philadel 
P- 77: 
*Proceedings American Philosophical Society, 1883, P. 324 
Bulletin, No, 37. 
3Journal Academy Nat. Sciences Philada., 1874, March. 
