PROFESSOR OWEN ON THE MEGATHERIUM. 
735 
met- and an-apophyses commence, suddenly, on the twelfth dorsal, the former (m) 
as broad compressed plates from the anterior two-thirds of the side of the neural 
arch, the latter (a) as short processes from the hinder border of the same arch. The 
metapophyses (ni) increase to the first lumbar, and after the second decrease to the 
sacral vertebrae : they again begin to increase in the caudals and attain great size in 
the third to the seventh of that series, in which latter vertebrae the zygapophyses 
have disappeared : but the metapophyses (see Plate LIII. fig. 62, a, c, m m) are con- 
tinued to near the end of the tail. The anapophyses (a) increase to the second 
lumbar, and rapidly decrease after the third ; they are obsolete in the last lumbar. 
The smaller Macropus Parryi, with the same vertebral formula, resembles the 
Great Kangaroo in regard to the accessory processes ; except that the anapophyses 
are relatively smaller and begin in the eleventh dorsal (Plate XLVII. fig. 13, d n, a) 
upon the diapophysis {d) ; passing in the twelfth to the back part of the neural arch ; 
they underlap the metapophyses {m) of the first four lumbar vertebrae and become 
mere rudiments in the two last {ib. ls and e, a). In both species of Kangaroo the 
diapophyses (d) continue to be developed in the last dorsal vertebrae, rendering the 
homologies of those of the lumbar series unmistakeable. 
In a Perameles lagotis, with d\3, Z 6, the metapophysis begins at the ninth dorsal 
vertebra, rapidly increases to the first lumbar, and continues large, though slightly 
decreasing in the last two lumbars : they are continued along the sacrum and a 
great part of the caudal vertebrae. There are no anapophyses in this species. 
Order Monotremata. 
The metapophyses are double, one behind the other, in the form of low tubercles, 
on each side of the neural arch of the third, fourth, and fifth dorsal vertebrae of the 
Ornithorhynchus paradoxus ; they become single on the sixth dorsal, and gradually 
increase in size to the twelfth : beyond this vertebra they increase in antero-posterior 
extent chiefly, and thus attain their maximum of size in the last dorsal and the two 
lumbar vertebrae ; they are continued throughout the sacral and to near the end of 
the caudal region. A rudiment of the anapophysis is discernible on the fourteenth, 
the fifteenth and sixteenth dorsal vertebrae, projecting backwards over the hole 
for the nerve at the side of the neural arch. 
Order Ungulata. 
Suborder Artiodactyla. 
Tribe Ruminantia. 
In the Musk-Deer {Moschus moschiferus) , with cZl4, Z5 (Plate XLVIII. fig. 14), a 
distinct metapophysis (m) begins to be developed above the diapophysis of the second 
dorsal, is midway between this and the prozygapophysis in the tenth dorsal, rises 
upon the outside of the prozygapophysis on the eleventh, attains its greatest length 
5 B 2 
