SINCLAIR: MARSUPIALIA OF THE SANTA CRUZ BEDS. 



335 



and, with the exception of Microbiotlieriitm, a minute opossum, have been 

 placed by Ameghino (1894, p. 108) in a suborder termed by him the 

 Sparassodonta, a group which he regards as referable neither to the creo- 

 donts, the placental carnivores, nor the carnivorous marsupials. A com- 

 parison of the so-called Sparassodonta with existing carnivorous marsu- 

 pials shows that they possess in common a large number of characters, 

 either confined entirely to marsupials, or peculiar to but few additional 

 orders. An examination of the following list will, it is believed, convince 

 the reader that the Sparassodonta are true carnivorous marsupials and 

 not worthy of subordinal rank. 



MARSUPIAL CHARACTERS OF THE SO-CALLED SPARASSODONTA. 



i. A typical marsupial dental for- 

 mula 2 i 



IHUld, 3 x 



l * 



3 4- 



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 fron- 

 tals and maxillae. 



1. The presence of three incisors 

 above and below is exceptional 

 among marsupials. A fourth 

 molar occurs in Otocyon and 

 Centetes among placentals. 



2. According to Ameghino, the 

 number of teeth having decidu- 

 ous predecessors is greater in 

 the Santa Cruz forms than 

 among existing marsupials but 

 less than in the placental Carni- 

 vora. 



3. A posterior broadening of the 

 nasals is characteristic of most 

 existing marsupials. The con- 

 tact between the maxillary and 

 frontal is more or less extensive 

 but may be reduced to zero as 

 in some specimens of TricJio- 

 sunts vulpecula. Certain of 

 the Creodonta (Harpagolestes, 

 Dromocyon, Mesonyx] also show 

 the posterior expansion of the 

 nasals. 



