386 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



approximately by comparison with adjacent portions of the column. The 

 depth of the anterior portion of the thorax is conjectural, as none of the 

 ribs in this region are preserved. The tail was probably long and heavy, 

 judging from the weight of its proximal portion. The legs are remarkably 

 short and the feet probably plantigrade or semi-plantigrade. 



Habits. The elongation of the fourth digit and the opposabilityof the 

 thumb point toward an arboreal habit. The loss of the opposable hallux 

 is an adaptation toward terrestrial progression, which does not necessarily 

 conflict with the view just stated, if we assume that these animals occupied 

 a place in the economy of nature similar to that now filled by the dasyures 

 and some of the smaller placental Carnivora. 



CLADOSICTIS LUSTRATUS (Ameghino). 



(Plates LII, Fig. 4 ; LIII, Fig. 10 ; LIV, Figs. 3, 4, 12 ; LV, Fig. i ; LVI ; LVII, Figs. I, la, 

 3, 5, 6; LVIII, Figs. i- 4 , 6 ; LIX, Figs. 7 - 7 l>; LXI, Fig. i.) 



Hathliacymis histratus Amegh. ; Enum. Sist. Especies Mamif. Fos. Pata- 

 gonia Austral, p. 7, 1887. 



Anatherium defossum Amegh. ; ibid. p. 8, 1887. 

 Hathliacymis defossus (Amegh.) Mercerat; Revista del Museo de La 



Plata, II, p. 53, 1891. 

 Proviverra trouessartii Amegh. ; Revista Argentina, I, pp. 149-150, fig. 



54. 1891. 

 Cladosictis trouessarti Amegh.: Enum. Syn., etc., pp. 131-132, figs. 50, 



51, 1894; Bol. Acad. Cordoba, pp. 386-388, figs. 50-51, 1894. 

 Cladosictis lateralis Amegh.; Enum. Syn., etc., pp. 132-133, 1894; Bol. 



Acad. Cord., p. 388, 1894. 



Judging from the number of individuals represented in the collection, 

 this must have been the most abundant of the Santa Cruz marsupial 

 carnivores. The two more or less complete skeletons on which the pre- 

 ceding account of the osteology of the genus is largely based (Nos. 15,046 ; 

 15,170) are from the Lower Santa Cruz beds, ten miles south of Coy Inlet. 

 Three very fragmentary skulls associated with a small amount of skeletal 

 material were collected by Mr. Hatcher at Lake Pueyrredon (see Narra- 

 tive, this series, Vol. I, p. 173). Several additional specimens were 

 obtained by Messrs. Hatcher and Peterson and Mr. Barnum Brown at 

 Coy Inlet and along the coast to the south of the Coy (Nos. 15,015 ; 15,704), 



