720 
PROFESSOR OWEN ON THE MEGATHERIUM. 
articulares superiores et inferiores,” These different processes offer many modifica- 
tions of size and shape, and a certain change of position and direction, when traced 
through the vertebrate series ; in the course of which comparison the anatomist meets 
with other exogenous processes, traceable with equal certainty from species to species 
and determinable under all their various modifications: wdienceit becomes necessary 
for the purpose of brief and clear description to indicate each of such processes by a 
single definite name, capable of being formed into an adjective to express the pro- 
perties or appendages of such processes 
The convenience of such terms will be admitted by the Human Anatomist who 
considers that the processes in question have, as yet, received no distinct substantive 
names in Anthropotomy ; and who knows, from Osteogeny, how vaguely some of the 
descriptive terms, as ‘transverse process,’ for example, are applied to parts obviously 
very different in their nature and constitution. The ‘ transverse process’ of a dorsal 
vertebra is a simple exogenous growth from the neurapophysis, commonly affording 
an articular surface for a rib ; the ‘ transverse process’ of a sacral vertebra -j- is an 
autogenous part, which continues distinct long afterbirth; the ‘transverse process’ 
of a cervical vertebra is partly exogenous, partly autogenous, consisting in fact of 
two distinct processes and a rudimental rib, but distinguished in Anthropotomy from 
other transverse processes only by ‘ being perforated.’ 
But if such common phrase of ‘transverse process,’ with a note of distinction, as 
that “it is perforated in the cervical vertebrae,” be sufficient for the exigencies and 
applications of Human Anatomy, it becomes quite inadequate and often totally inap- 
plicable to the answerable parts in the lower animals : in the Crocodile, for example, 
the cervical rib is much more developed and maintains constantly a free articulation 
by a ‘ head’ with a well-developed inferior transverse process (‘ radix antica,’ Soemm.), 
and by a ‘ tubercle’ with an equally distinct superior transverse process (‘ radix pos- 
tica,’ Soemm.). In the Wombat (Plate XLIV. fig. 12), the Hare, the Pig, and most other 
quadrupeds, the process of the lumbar vertebrse consists of an exogenous 
base and an autogenous apex, this apex being, as Theile and Muller have 
shown, a rudimental rib like the autogenous part of the transverse process in the 
neck. 
In entering upon the descriptions of the extinct species of the Reptilian class §, the 
most varied, extraordinary and heteroclite, as Cuvier justly remarks, of any of the 
* This I have done for some years past in my Lectures at the Royal College of Surgeons, in the ‘ Catalogue 
of the Human and Comparative Osteology in the Museum of the College,’ and in some of my published me- 
moirs : ase. y. On the Plesiosaurus 7nacrocephalus, Geological Transactions, 4to, 1838. On the Anatomy 
of the Male Aurochs {Bison europceus), Proceedings of the Zoological Society, November, 1848, p. 131. 
-f “ Laterales partes, quse processus transversos coalitos reprsesentant,” Soemm. op. cit. t. i. p. 271. 
I Archiv fiir Anatomic und Physiologic, Jahrg. 1839. Vergleichende Anatomic der Myxinoiden, in ‘Berlin 
Abhandlungen,’ 1836, p. 304. 
§ Reports of the British Association, 1839. 
