PROFESSOR OWEN ON THE MEGATHERIUM. 
723 
tions in my ‘Anatomy of the Male Aurochs,’ in which, as in most other Ruminants, 
the anapophysis is not present The process which is developed, sometimes singly, 
sometimes in pairs, from the under part of the centrum in some mammals and in 
most birds and reptiles, I have called ‘ hypapophysis'f.' 
I propose in the first place to trace the homologies and to indicate the chief modi- 
fications of the metapophyses and anapophyses in the mammalian class, and thereby 
to vindicate their title to distinct names, and demonstrate the utility, if not the 
necessity, of such signs for parts so constant in existence and so variable in character 
in a great proportion of that class. I may remark, also, that as 1 shall frequently 
have to allude to the anterior as distinct from the posterior zygapophyses, I shall 
call the former ‘ prozygapophysis,’ and use the term ‘ zygapophysis ’ simply to signify 
the posterior pair. 
* “ With regard to the vertebrae of the trunk of the Aurochs, I may remark, that the only accessory pro- 
cess in addition to the ordinary zygapophyses and diapophyses is the ‘ metapophysis,’ which appears as a stout 
tubercle above the diapophysis in the middle dorsals, and gradually advances and rises upon the anterior zyg- 
apophyses in the posterior dorsal and lumbar vertebrae. This process is developed to an equality of length with 
the spinous processes in the Armadillos. It is commonly associated with another accessory exogenous process, 
to which I have given the name ‘ anapophysis ’ in the Catalogue of the Osteological Series in the Royal Col- 
lege of Surgeons. This process, which in most of the Rodentia rises, at first, in common with the metapo- 
physis, as a tubercle above the diapophysis, separates from the metapophysis as the vertebrae approach the 
pelvis, and in the lumbar series the anapophysis is seen projecting backwards from the base, or a little above 
the base of the diapophysis, its office being usually that of underlapping the anterior zygapophysis of the suc- 
ceeding vertebrae and strengthening the articulation, whence Cuvier has alluded to it as an accessory articular 
process ; hut its relation to the zygapophysial joint is an occasional and not a constant character. The tenth 
dorsal vertebra of the Saw-toothed Seal, Leptonyx serridens, affords a good example of well-developed met- 
apophyses ; they are also large in most of the trunk-vertebrse of the Ta 2 iir. The anapophyses are well-de- 
veloped in the anterior lumbar vertebrae of the Hare and Rabbit.” — Proceedings of the Zoological Society of 
London, November 1848. 
In a volume of Swedish Transactions, for 1848, Prof. Retzius has a paper, illustrated by woodcuts, on the 
modifications of some of these processes in the Class Mammalia. I have been recently favoured with a copy of 
the memoir by the learned author, bearing date ‘ Stockholm, 1850,’ on the title-page, and received since the 
greater part of this paper was written and all the materials for it collected, which has been a wmi'k of some 
years past ; but I regret that my ignorance of the Swedish language has prevented my profiting by the remarks 
of the estimable anatomist. In the cuts the metapophyses are called ‘ processus mammillares,’ the anapophyses 
‘ processus accessorii.’ 
[In a German translation of this memoir, kindly transmitted to me by Prof. Retzius since the present paper 
was in type, the following passage is added to the original : — 
“ (Zusatz des Verfassen; aus briefficher Mittheilung desselben au den Uebersetzer vom 5 August 1850. — 
Nachdem diese Abhandlung bereits gedruckt war, hat der Verf. erfahren, dass Prof. Richard Ow’en in 
London schon i. J. 1848 (Proceedings of the Zoological Society) den Pr. mammillares sowohl als den Pr. ac- 
cessorii, eigene, einfache Benennungen gegeben hat. Er nennt namlich die ersteren oder Pr. mammillares 
‘ Metapophyses’ und die letzteren oder die Pr. accessorii ‘ Anapophyses,’ von perci inter, und iiv'a retro, die 
ersten als zwischen den Diapophyses und Zygapophyses Owen liegend ; die letzteren als mehrentheils nach 
hinter gerichtet.”) p. 449.] — R. O. October 27th, 1851, 
"j* From vTTo sub, airofoais processus. 
