318 PROF. OWEN ON THE CLASSIFICATION 
beyond them but not in the same degree, nor are they separated from them by an in- 
terval as in the upper jaw. The canines are relatively smaller than in the Dasyures. 
The spurious molares present a similar form, but the third is much smaller and simpler 
than the two preceding ones. The true molars resemble in their structure those of the 
Dasyures. The general character of the dentition of these small Marsupials approxi- 
mates to the insectivorous type as exhibited in the Shrew, Hedgehog, &c., among the 
placental Mammalia ; and corresponds with the food and habits of the species which thus 
lead from the Zoophagous to the Entomophagous tribes. 
Other links which once bound these tribes more closely together are now lost, and 
are indicated only by the few fossil remains which have rendered the Stonesfield oolite 
so celebrated. One of these extinct genera, which I have called Phascolotherium, pre- 
sents the same numerical dental formula, apparently, as in the Thylacinus and Phasco- 
gale ; but, if another incisor existed in each ramus of the lower jaw, as seems to be in- 
dicated by a fossil, fe ee dentition would agree with that of the genus Didelphys. 
rp? Pt 
Incisors 2 a = canines ;—,; premolars ;—,; molars 7—7. 
or 
4—4 
The incisors and canines are Sey by vacant interspaces, and occupy a large 
proportion of the dental series : the true molars resemble those of Thylacinus. 
Tribe I. ENTOMOPHAGA. 
This is the most extensive and varied of the primary groups of the Marsupial order. 
In the system of Cuvier, the species of this tribe are united with those of the preceding 
to form a single group characterized by the presence of long canines and small incisors 
in both jaws ; but in most of the Entomophagous genera of the present classification, the 
canines present a marked inferiority of development, and the species are consequently 
unable to cope with animals of their own size and grade of organization, but prey, for 
the most part, upon the smaller and weaker classes of invertebrate animals. Their in- 
testinal canal is complicated by a moderately long and large cecum; and, while in the 
Sarcophaga, the feet are constructed, as in the ordinary placental Digitigrades, they pre- 
sent in the present tribe a variety of well-marked modifications, according to which the 
species may be arranged into ambulatory, saltatory, and scansorial groups. 
a. AMBULATORIA. 
The only known existing representative of this family is the animal described by 
Mr. Waterhouse, which constitutes the type of his genus Myrmecobius, of which the fol- 
lowing is the remarkable dental formula : 
3 pl 
53 molars a De 
4—4 iI —_ 
Incisors canines ;—; ; premolars 7—5 : 
ia? 1— 
