358 PROF. OWEN ON A NEW SPECIES OF STHENURUS. [Apr. 17, 
it is with the characters of the long trenchant premolars, the retained 
canines, the produced anterior incisors, and the palatal vacuities, an 
addition to those evidences of the departure of the genus from Ma- 
cropus proper and Sthenurus, and of its approximation to Hypsi- 
prymnus. 
It may be that the grounds of my homologies of the teeth of 
Macropodidz are not deemed conclusive. They are as follows, and 
I am open to any objections which may have barred Prof. Garrod’s 
acceptance of them. 
In the subjoined cut, A represents the dental series, deciduous 
and permanent, exposed in the right mandibular ramus of a young 

Pig (Sus scrofa, L.); B represents the same in a young Kangaroo 
(Macropus major, Shaw). 
In place of the incisors di 1, di 2, di 3, and of the canines, ¢, in the Pig 
(A), we have the single incisor, 7, in the Kangaroo (B), which may 
be the homologue of 71 in the Pig. Of the tooth di in the 
Pig there is no homologue in the Kangaroo. The small foremost 
molar, d2, in the Kangaroo, I view as the homologue of d2 in the 
Pig; but in the Pig there is a vertical successor, p 2, which is not 
developed in the Kangaroo. The tooth d3 in the Kangaroo is the 
homologue of d3 in the Pig: in both it has a vertical successor—a 
true ‘ premolar,’ p32, which displaces it usually, in Macropus major, 
a short time after the fall of d2; and this premolar rises into place, 
like pin the Pig, without displacing the tooth d4. Beneath d4, 
in the Kangaroo, there is no vertical successor—no p 4 as in the Pig; 
and in this respect d4 in the Kangaroo resembles d2. These 
homologies being determined, or accepted, those of m1, m2, m3, with 
the molars similarly symbolized in the Pig, follow as a matter of 
