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PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
riorly in both upper and lower series. Talonid of M ? inclosing a small basin- 
shaped area with a single high point on its posterior rim. Palate imperforate. 
Mandibular symphysis ligamentous. Hallux reduced. Terminal phalanges 
uncleft, laterally compressed and pointed. Cladosictis . 
(Miocene, Santa Cruz formation, Patagonia, C. lustratus , C. petersoni.) 
3 . Dental formula f, 1, f, |. Protocone well developed on all the upper molars. 
M^ with protocone inclosing a basin-shaped area, paracone and antero-external 
style large, metacone vestigial or absent. Upper premolars increasing regularly 
in size posteriorly ; median and posterior lower premolars subequal. Talonid 
of Mj large and strongly bicuspidate. Palate imperforate. Mandibular sym- 
physis ligamentous. Hallux large and opposable. Terminal phalanges later- 
ally compressed and pointed, without clefts. Aniphiproviverra. 
(Miocene, Santa Cruz formation, Patagonia, A. masaniana, A. minuta .) 
( b ) Alisphenoid bulla absent. 
1 . Dental formula ^ ? , Protocone well developed on MJ-, and M-2-, absent on 
M-. M^ with vestigial protocone and metacone. Posterior premolar not greatly 
enlarged, in the inferior series not exceeding the median premolar in size. 
Talonid of M^- small and basin-shaped, with a single high cusp on its posterior 
rim. Palate imperforate. Mandibular symphysis fused. Hallux reduced, not 
supporting phalanges. Terminal phalanges laterally compressed, sharply 
pointed, and slightly cleft at tips. Prothylacynus . 
(Miocene, Santa Cruz formation, Patagonia, P. patagonicus.) 
B. Skull brachycephalic. 
( a ) Alisphenoid not dilated to form a bulla. 
1 . Dental formula |, i, |-, Protocone on upper molars reduced. M-4 bicuspidate 
with paracone and antero-external style. Posterior premolars greatly enlarged. 
Talonid of Mj with single conical cusp. Palate imperforate. Mandibular sym- 
physis fused. Hallux unknown. Terminal phalanges round, blunt, and broadly 
fissured at the tips. Borhycena. 
(Miocene, Santa Cruz formation, Patagonia, B. tuberatci, B. excavata.) 
The determination of the marsupial affinities of the Santa Cruz dipro- 
todonts rests almost entirely on their close resemblance to Ccenolestes . 
The discussion of the classification adopted is more conveniently post- 
poned to a later chapter, but it may be remarked in passing that all are 
referred to one family, the Caenolestidae, so named from its best known 
and only surviving representative, Ccenolestes . 
