749 
PROFESSOR OWEN ON THE MEGATHERIUM. 
and mortises’ is superadded below the others, in some Edentates, by the special 
development of the anapophyses and of parapophyses. 
I know not how these complex but constant characteristics differentiating the 
Ophidian and Mammalian vertebrae could be intelligibly made known without the 
use of ‘ names ’ for the parts ; and, as I trust, that I have shown the parts to be not 
mere subdivisions of the diapophyses, but constant, characteristic, and independent 
processes, definite names for them cannot be reasonably deprecated as unnecessary*'. 
Before leaving this part of my subject, I may point out a few of the modifications 
of the exogenous processes of the vertebrae, by which different genera of Ophidia 
may be distinguished. 
In the genus Coluber (Plate LI., fig. 29-32), the diapophysis, besides develop- 
ing the articular tubercle {d) for the rib, sends a long process {d") outwards above 
that tubercle, between it and the prozygapophysis (a), and a very short process {d’), 
like a parapophysis, downwards below that tubercle: the neural spine {ns) is low in 
proportion to its antero-posterior extent : the zygosphenal surfaces (;s .y) ai’e nearly 
vertical, and the zygantra (z a) are wide apart : the hypapophysis (fig. 32, hy) beyond 
the anterior fourth part of the vertebral column is reduced to a straight ridge, and 
is not produced posteriorly. 
In the Sea-Serpent {Hydrus) (fig. 33.), the diapophysis also sends out a process 
above and below the articular tubercle ; but that which seems to underprop the 
zygapophysis, does not extend so far out as in the Coluber. The neural spine 
(fig. 33, ns) is higher in proportion to its antero-posterior extent: a very small hyp- 
apophysis projects below the articular ball of the centrum, and a low ridge is con- 
tinued from it along the under part of the centrum. 
In the Naja or Cobra di Capello, the neural (fig. 34, ns) spine is lower, but the 
hypapophysis {hy) is longer than in either of the preceding genera. The diapophysis 
presents a well-marked articular tubercle (fig. 35, d) upon its upper part, and both 
the upper {d”) and lower {d!) processes are well-marked, although the former is shorter 
than in the genus Coluber. 
The Rattle-Snake {Crotalus) (fig. 36-39) is remarkable for the development of 
the hypapophysis {h) to an equal length with the neural spine {ns) throughout the 
vertebrae of the trunk ; such development being restricted to the anterior vertebrae 
in most other genera : and any single vertebra might be distinguished from an ante- 
rior trunk-vertebra of a Boa or Python, for example, by the following characters : — 
The diapophysis developes a small hemispheric tubercle {d) from its upper convexity ; 
and a process {d’) from its under part extending downwards and forwards below 
* See the criticism in ‘Proceedings of the Zoological Society,’ December 12, 1808, in which the author,— 
“ Understanding that Professor Owen had proposed names for these mere subdivisions of the diapophyses, 
strongly deprecated the overloading this difficult part of anatomy with unnecessary names," p. 146 ; and yet he 
proceeds “to animadvert upon Cuvier and M. de Blainville for having neglected to describe them,” as if 
they could be intelligibly described without determinations and names. What is truly to be deprecated is the 
unnecessary change of names when once rightly applied. 
MDCCCLI. 5 D 
