734 
PROFESSOR OWEN ON THE MEGATHERIUM. 
of the so-called ‘ transverse process’ is plainly demonstrated. The diapophysis, more- 
over, is not suppressed on the last dorsal vertebra as in some of the Quadrumana, 
Carnivora and Rodentia. The serial homology of the transverse processes of the lumbar 
vertebrae is here, therefore, manifested in the most unequivocal way ; both metapo- 
physes {771) and anapophyses (a) coexist with diapophyses (d) in the last four dorsal 
and the first three lumbar vertebrae. So that, whether the metapophysis or the an- 
apophysis be the part called ‘ tubercle’ by some Anthropotomists, neither of them 
is in the lumbar vertebrae, the process named ‘ transverse’ in the thoracic vertebrae ; 
that process, to which I restrict the name ‘ diapophysis,’ is continued distinctly into 
the lumbar region, and is there lengthened out by a superadded ‘ pleurapophysis,’ 
which is ossified from a distinct centre in the Wombat, but is not so ossified in the 
human skeleton, in which only a mere epiphysis, like that at the extremity of the 
spinous process, is superadded to the end of the transverse process of the lumbar 
vertebrae*. 
In the skeleton of the Great Kangaroo {Macropus Tnajor), with d 13, I 6, both 
* The author of the article ‘Skeleton’ in the Cyclopaedia of Anatomy and Physiology, Part XXXV., 
March 1839, cites, p. 628, the following passage from my work on the Archetype and Homologies of the Ver- 
tebrate Skeleton ; — “ Each of the five succeeding segments is represented by the same elements coalesced, that 
constitute the so-called dorsal vertebra ; they are called lumbar vertebrae ; they have no ossified pleurapophyses,” 
with the following comment: — “Professor Owen’s ‘pleurapophysis’ is the rib or costal appendage of his 
typical vertebra. While he states, therefore, that the lumbar vertebra has no pleurapophysis, he means that it 
has no rib or costal piece. This oversight (which, with all respect, I believe it to be) has arisen from the 
evident error of mistaking the lumbar transverse process as being the counterpart or homologue of the dorsal 
transverse process, which, if such were the case, would leave the lumbar vertebra without a rib.” The passage 
so commented on is taken from a ‘ Section’ of my work treating of the specialities of the Human Skeleton ; in 
the ‘ Section’ treating on lumbar vertebrae in general, I state, — “ The lumbar vertebrae, which in some mammals 
show, in the foetal state, distinct rudiments of pleurapophyses more minute than those in the neck, have them 
soon anchylosed to the extremities of the diapophyses, which are thus elongated,” p. 94. No one proposing 
fairly to criticise my opinions on the transverse process of a lumbar vertebra in general, ought to have repre- 
sented them by a quotation of a description of the lumbar vertebra of a particular species. But taking the 
passage upon the human skeleton, as cited above, the conclusion of the Critic that I “ leave the lumbar vertebra 
without a rib,” can only be sustained by the omission of a word in that passage. What I do state is, that, in 
them, “ they have no ossified pleurapophyses.” Now in a previous part of the work quoted from, it is shown, 
that a vertebral element may exist in three states, ‘ fibrous,’ ‘ cartilaginous,’ ‘ osseous,’ and that its absence was 
not to be assumed merely because it had not passed into the bony stage. I have never met with a human lumbar 
vertebra showing the transverse process lengthened out by a distinct autogenous ossification, meriting, like 
that of the Wombat, Plate XLVII. fig. 12, l 1 , to be regarded as a pleurapophysis : the whole is an exogenous 
outgrowing diapophysis, with a minute epiphysis, which begins to be ossified about the age of sixteen, and is 
comparable in my opinion with that at the extremity of the metapophysis and neural spine. As to the opinion 
that the transverse process of the dorsal vertebra is homologous with the ‘ tubercle ’ of the lumbar vertebra, 
w'hether by ‘ tubercle’ is meant the metapophysis or the anapophysis, I need only refer to those skeletons of 
mammalia, in which, as in the Wombat, Kangaroo and Dasyure, the true diapophysis is not suppressed on the 
last dorsal vertebra, in order to ensure a conviction in every impartial observer that the exogenous part of the 
transverse process of the lumbar vertebra is the serial homologue or tallying part with the diapophysis, or part 
of the transverse process supporting the rib, of the dorsal vertebrae. 
