334 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 



Before proceeding farther, the writer desires to express his indebted- 

 ness to Professor Scott for permission to study this important group and 

 for much helpful criticism and encouragement during the progress of the 

 work. A number of photographs of type specimens in the Ameghino col- 

 lection taken by Professor Scott have proved of great value in the study 

 of the diprotodont forms. Indeed, without their help, it would have been 

 impossible to be at all certain regarding the determination of many of the 

 species. The American Museum collection of Santa Cruz marsupials, 

 especially rich in diprotodonts, was placed at the writer's disposal by 

 Professor H. F. Osborn, who has also contributed much valuable informa- 

 tion regarding marsupial characters in general. Several important sug- 

 gestions by Dr. W. D. Matthew and Mr. Charles Knight have been 

 incorporated in the drawings of the restored skeletons of Frothy lacynus, 

 Borliycena and Cladosictis (PI. LXI). Dr. J. A. Allen has kindly per- 

 mitted the examination and illustration of a skull of Ccenolestes obscurus 

 in the collection of the American Museum of Natural History (PI. 

 LXIII, figs. 14-14^). To Dr. Oldfield Thomas, of the British Museum, 

 the writer is indebted for the loan of valuable osteological material illus- 

 trating the skeleton of Thylacynus, without which it would have been im- 

 possible to work out in a satisfactory manner the relationships of the 

 Santa Cruz carnivorous marsupials. Liberal use has been made of this 

 material in the figures presented in the accompanying text and plate 

 (PI. LXV, figs. \-\b}. 



CLASSIFICATION OF THE SANTA CRUZ MARSUPIALS. 



As among recent marsupials, two suborders may be recognized, agree- 

 ing in every respect with the Polyprotodontia and Diprotodontia. It has 

 seemed advisable to retain the major subdivision of the order based on 

 dental characters rather than to follow the recent classification proposed 

 by Bensley (1903) in which dental characters are subordinated to foot 

 structure, because practically nothing is known of the feet in the Santa 

 Cruz diprotodonts, and what little is known of the feet in Ccenolestes, their 

 nearest living ally, adds to the confusion already existing in the classifi- 

 cation of the Marsupials by combining a non-syndactylous foot with a 

 diprotodont dentition. 



The Santa Cruz representatives of the Polyprotodontia are carnivorous, 



