Sinclair: marsupialia of the santa cruz beds. 381 
In the remaining cervicals the neural spines increase regularly in 
robustness and probably also in height, although this can not be deter- 
mined, owing to the fracturing of their extremities. The inferior lamellae 
of the transverse processes are more wedge-shaped than in Thylacynus , 
resembling rather this region in Borhyamci , and, as in that genus, the dia- 
pophyses are fully differentiated on the fourth cervical. The transverse 
processes of the seventh cervical are perforated by the arterial canal. The 
centra are all heavily keeled inferiorly, but, owing to imperfect preserva- 
tion, it can not be determined whether the keels decrease in depth in the 
posterior cervicals, as in Prothylacynus and Thylacynus. The upper sur- 
face of the neural arch of the third cervical is perforated on the left side 
by a rather large foramen. A smaller corresponding foramen occurs 
somewhat farther back on the right side. Small foramina may occupy 
similar positions in some of the other cervicals. The foramina piercing 
the lateral walls of the neural arches of the second to the seventh cer- 
vicals, which are so prominent in Thylacynus (text-fig. 5, d) t are present 
in some of the cervicals of Cladosictis and absent in others. 
The dorso-lumbar formula is apparently nineteen, although this can 
not be accurately determined, owing to the incomplete state of preserva- 
tion of the column. The neural spines of the anterior dorsals are high 
and broad, but gradually decrease in both dimensions to the tenth, or anti- 
clinal vertebra. Beyond this point, the strong backward slope of the 
spines changes abruptly to a forward direction. Metapophyses are devel- 
oped on the tenth dorsal, and are prominent as far posteriorly as the sec- 
ond lumbar, beyond which they begin to decrease in height. Ana- 
pophyses also appear on the tenth dorsal and increase in size posteriorly 
until the fifth lumbar is reached, when they become smaller. 
The lumbars (Plate LVII, fig. 6) are six in number. They have heavy 
neural spines strongly inclined forward, with broad tips flattened superiorly, 
and wide, thin transverse processes, with a forward and downward curva- 
ture. The long, keeled centra increase regularly in size posteriorly. In 
the first, second and third lumbars, the keels are bifid posteriorly, inclos- 
ing a more or less flattened, wedge-shaped area. The prezygapophyses 
overlap the outer margin of the postzygapophyses, producing an inter- 
locking articulation. This applies also to the anterior zygapophyses of 
the thirteenth dorsal. 
The sacrum (Pis. LVII, figs 1, la ; LVIII, figs. 1, 7, 7 a) is composed 
