382 
PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 
of two vertebrae more completely fused than in Thy lacy nus and lacking 
the dorsal intervertebral fontanelle so conspicuous in the latter genus. 
The spines are remarkably feeble in contrast with the heavy spine of the 
last lumbar. The auricular processes are confined almost entirely to the 
first sacral. The centra are keeled inferiorly, the first having a single low 
median keel and the second a pair of parallel keels. 
The caudals are remarkably heavy. Those associated with No. 15,170, 
which have been reproduced in the figures (Pis. LVII, fig. 5 ; LXI, fig. 
1), are interpreted as the third to the tenth. The proximal ones are 
short, with stout, posteriorly directed transverse processes. The centra of 
the more distal caudals increase in length and the transverse processes 
become wider and shorter. The neural canal is complete as far back as 
the tenth caudal. It is not possible from the material at hand to deter- 
mine the length of the tail, but judging from the size of the caudals pre- 
served, it was probably long and heavy. From analogy with Thy lacy nus, 
it has been restored with a vertebral formula of twenty-three. Chevrons 
are present between the third and fourth caudals and are represented either 
by the small hatchet-shaped pieces themselves, or by surfaces for their 
attachment, as far back as the caudal series is preserved (PI. LXI, fig. 1). 
A few ribs are associated with both specimens of C. lustratus. The 
anterior ribs (PI. LVIII, fig. 3) have more cylindrical shafts than in Thy- 
lacynus. The posterior ribs are slender and sub-round in section. 
Appendicular Skeleton. — The scapula (PI. LVII, figs. 2-3) corresponds 
more closely with that of Pvothylacynus than with the corresponding ele- 
ment in Bovhymia or Thylacynus. The neck is short, the glenoid cavity 
oval in outline and moderately deep and the coracoid prominent, with its 
anterior margin strongly inflected. In shape the scapular fossae are much 
as in Pvothylacynus. The spine is high, but its free border has been 
somewhat fractured in both specimens, destroying the acromion. The 
foramen which perforates the margin of the suprascapular notch in Thy- 
lacynus appears in Cladosictis some distance posterior to the coracoid 
border. 
No trace of a clavicle has been found and its introduction in the resto- 
ration (PI. LXI, fig. 1) is conjectural. It may have been rudimentary and 
not attached to the acromion, as in Thylacynus. 
The humerus (PI. LV, figs. 2, 2 a) is short and heavy, resembling de- 
cidedly that of Pvothylacynus , but differing in the less prominent epicon- 
