PROFESSOR OWEN ON THE MEGATHERIUM. 
745 
ceeding vertebrae, in the three last of which the diapophysial element of the process 
stands out distinctly and strongly. In the seventh cervical this element alone is de- 
veloped, and the transverse process is accordingly said to be imperforate. A metapo- 
physial tubercle is developed from the outer side of the prozygapophysis of the five 
last cervicals. The diapophyses of all the dorsals present an articular surface for the 
tubercle of the rib. The metapophysial tubercle is continued from the cervical to the 
dorsal region, appearing there upon the upper part of the diapophyses of the first 
dorsal; it continues increasing in size and length to the thirteenth dorsal, where it 
begins to shift its position, and in the remaining dorsals projects midway between the 
diapophysis and zygapophysis. In the fourteenth dorsal the metapophysis also in- 
creases suddenly in breadth, and developes an articular surface from its inner side to 
join an accessory posterior zygapophysis, as well as an articulation upon its fore and 
under part for the anapophysis of the preceding vertebra. In the fourteenth dorsal 
the anapophysis suddenly acquires increased length and breadth, with a distinct 
articular surface upon both its upper and under part, the upper one articulating with 
the metapophysis, the under one with the parapophysis of the succeeding vertebra. 
Thus there are not fewer than sixteen co-adapted articular surfaces, in addition to 
those for the head and tubercle of each rib and the articulations between the ends of 
the centrum of one and the same vertebra. In the first lumbar vertebra the diapo- 
physis increases in thinness and decreases in length, presenting the form of a de 
pressed plate ; the other processes with thin articular surfaces are retained in both 
lumbar vertebrae. Parapophyses and metapophyses are also developed from the fore- 
part of the first sacral vertebra, together with another accessory process extending to 
the parapophyses, projecting from the fore-part of the diapophyses, and presenting an 
articular surface to a corresponding accessory articulating process for the anapo- 
physis of the last lumbar. The neural spines of the five sacral vertebrae have 
coalesced into a continuous ridge, on each side of the base of which are the tuber- 
cular representations of the metapophyses. The transverse processes of the last 
sacral are enormously expanded, and develope from their under part a broad rough 
prominence for syndosmosis with the anterior tuberosity of the ischium. The posterior 
and ordinary tuberosity of that bone projects freely outwards beneath the transverse 
processes of the first caudal. The metapophysial tubercles begin to be developed 
from above the prozygapophyses from the first to the eighteenth caudal, beyond which 
the metapophyses exclusively represent the articular processes. The broad transverse 
processes have an accessory tubercle near their extremities, as far as the sixth caudal ; 
at the seventh they are notched at their extremities, and the notch deepens until it 
divides the diapophyses into two in the eighteenth vertebra, and so on till they disap- 
pear at the end of the tail. Htcmal arches are articulated between the vertebral 
interspaces of most of the caudals. 
In the Great Ant-eater {Myj'mecophaga juhata) , with d 15, I 3, the transverse pro- 
cesses of the atlas are pierced in two places obliquely at the fore-part of the neural 
