76 SINCLAIR— FAUNA OF SANTA CRUZ BEDS. [April i 3j 



The Santa Cruz thylacynes are short-legged animals with large 

 heads, long necks and heavy tails. These characters are well 

 shown in the accompanying restorations of Prothylacynus patagoni- 

 cus and Cladosictis In stratus (Plates land II) reproduced from the 

 forthcoming Volume IV of the Reports of the Princeton Univer- 

 sity Expeditions to Patagonia. In addition to the characters 

 already mentioned, the following are worthy of notice : 



i. The facial region of the skull is short in proportion to the 

 length of the cranium. The brain case is small and greatly con- 

 stricted postorbitally. The orbits are placed much further forward 

 than in the Dasyuridre, opossums, or Thylacynus. The jugal arches 

 are robust and broadly expanded, and the sagittal and lambdoidal 

 crests well marked but not very high. The palate lacks the vacui- 

 ties present in all existing carnivorous marsupials, but is perforated 

 by a number of accessory palatine foramina. Between the molars, 

 the margin of the palate is depressed into deep hemispherical fossa; 

 for reception of the tips of the lower teeth when the mouth is 

 closed. The occiput is semicircular in outline in contrast with its 

 triangular shape in the dasyures, Sarcophtfus and Thylacynus. The 

 lachrymal canal opens well within the orbital rim. In the majority 

 of living marsupials, the opening of the lachrymal duct is placed 

 either on or external to the orbital rim. Thylacynus is transitional 

 between these two types of structure in that it possesses a double 

 lachrymal perforation, one branch of the canal opening without 

 and the other within the orbit. Borhycena and Prothylacynus, 

 resemble Sarcophilus in the fusion of the mandibular symphysis. 

 In the remaining genera the symphysial union is ligamentous. 



2. The molars are of the same type as in Thylacynus, differing 

 principally in the greater reduction of M 4 -, the loss of all the styloid 

 cusps except the antero-external, and the character of the heel of 

 the last lower molar, which may be either small and conical, 

 basin-shaped or bicuspidate. The premolars are unreduced in 

 number, and usually increase in size posteriorly in both series. 

 The canines are long, sharply pointed and slightly curved in the 

 smaller genera. In Borhycena the fang is swollen and the point 

 short and blunt. The incisors in Borhycena are reduced to f , an 

 exceptional formula among marsupials in that the number above 

 and below is the same. In Amphiproviverra the median pair are 

 conical and approximated at the tips as in Dasyurus and DiJcl- 



