74 SINCLAIR— FAUNA OF SANTA CRUZ BEDS. [April 13. 



and styloid cusps in the upper teeth. In the Dasyuridre, these 

 styles are almost as high as the outer cusps of the trigon. The 

 family name, based on the Tasmanian marsupial wolf Thylacynus, 

 was proposed by Buonaparte in 1838, and may very properly be 

 extended to include the related South American forms. 



The Santa Cruz thylacynes were predatory carnivores. An indi- 

 cation of their pugnacious habits is afforded by the traces of wounds 

 received in fighting, which are found occasionally on the skull and 

 mandible. 



These carnivores have been placed by Ameghino in a sub-order 

 named by him the Sparassodonta, a group which he regards as refer- 

 able neither to the creodonts, the placental carnivores, nor the car- 

 nivorous marsupials. That the so-called Sparassodonta are true 

 marsupials, and not worthy of sub-ordinal rank, is fully apparent 

 from the following characters, which they possess in common with 

 existing marsupial carnivores : 



1. A typical marsupial dental formula, ^, \, f, \. 



2. The number of successional teeth is reduced below that char- 

 acteristic of the placentals. 



3. The nasals are broad posteriorly, excluding from contact the 

 frontals and maxillas. There is usually a small contact in existing 

 carnivorous marsupials. A similar broadening of the nasals is ob- 

 servable in Mesonyx, Harpagolestes and Dromocyon among the 

 Creodonta. 



4. Anteroposterior shortening of basis cranii. 



5. Lachrymal spreading out on the face ; lachrymal duct within 

 the orbit. An internal opening of the lachrymal duct is observable 

 in Tliylacynus. 



6. Inflected mandibular angle. 



7. Excavation of the premaxillse for reception of the tips of the 

 lower canines as in the dasyures, Thylacynus and the opossums. 



8. Basisphenoid and alisphenoid ridged as in existing marsupial 

 carnivores and unlike the structure of this region in the placentals. 



9. Posterior extension of the malar bar to form the pre-glenoid 

 process. 



10. Posterior border of palate thickened. This structure is 

 observable also in certain creodonts. 



11. Posterior border of palate perforated by a large foramen on 

 either side of the posterior nares. 



