CAENOLESTIDAE 219 



Proborhyaena antiqua Ameghino 



? Borhyaena antiqua Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 655. 

 Prolx>rhyaena 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 

 genera of tiny marsupials with the dental formula \\*\ ; 

 the lower fourth premolar enlarged into a sectorial tooth; 



