CAENOLESTIDAE 219 
Proborhyaena antiqua Ameghino 
? Borhyaena antiqua Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 655. 
Proborhyaena antiqua Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 502. 
This species is known only by a single canine 100 mm. 
long, of which but 15 mm. belongs to the crown. Its 
antero-posterior diameter is 14 mm., the transverse 12 mm. 
It seems to me very doubtful whether this is a valid species. 
Caenolestidae 
This family, based on the living genus Caenolestes, is 
represented in Tertiary times in Patagonia by three sub- 
divisions, Palaeothentinae, Garzoninae, and Abderitinae. 
While diprotodonts, as far as known, the family is in strong 
contrast to the Australian diprotodonts in that there is no 
sign of syndactylism in the pes. The American forms are 
characterized by four subequal upper incisors, a normal 
canine, the first three premolars vestigal, while the fourth 
is either normal or enlarged into a sectorial tooth. The 
three molars are progressively smaller from the front back. 
The first lower incisor is greatly enlarged and procumbrent, 
the remaining incisors, the canine, and the anterior pre- 
molars being vestigal though usually present. Premolar 
4 is enlarged and sectorial in most genera, and the molars 
as in the upper jaw progressively smaller. 
For the practical purposes of this paper the subfamilies 
are distinguished as follows: 
Caenolestinae, lower pm. 4 not developed into a sectorial tooth. 
Palaeothentinae, lower pm. 4 is developed into a sectorial tooth. 
Abderitinae, lower pm. 4 is developed into a sectorial tooth and striated. 
Palaeothentinae Sinclair. 
(=Epanorthidae Ameghino) 
This group or subfamily was established to hold several 
: : é; ? 
genera of tiny marsupials with the dental formula 77); 
the lower fourth premolar enlarged into a sectorial tooth; 
