386 
PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 
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 opposability of 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. 1 ; LVI ; LVII, Figs. 1, 1 a, 
3, 5, 6; LVIII, Figs. 1-40, 6 ; LIX, Figs. 7-7*; LXI, Fig. 1.) 
Hathliacynus lustratus Amegh. ; Enum. Sist. Especies Mamif. Fos. Pata- 
gonia Austral, p. 7, 1887. 
Anatherium defossum Amegh. ; ibid. p. 8, 1887. 
Hathliacynus 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. 1 31- 132, figs. 50, 
51, 1894; Bob Acad. Cordoba, pp. 386-388, figs. 50-51, 1894. 
Cladosictis lateralis Amegh.; Enum. Syn., etc., pp. 132- 133, 1894; Bob 
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. 1 5,046 ; 
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. 1 5,015 ; 1 5,704), 
