268 MR. ST. GEORGE MIVART ON THE | Apr. 28, 
greater number of the caudal vertebree, and in the genera Proteus, 
Menobranchus, and Siren (fig. 18) in the cervical vertebra also. 
Generally the fully developed transverse processes are more or less 
cylindrical or somewhat compressed from before backwards, their long 
diameter, however, extending outwards and more or less (fig. 15, c) 
obliquely backwards, as in Menopoma, Cryptobranchus, Salamandra, 
&c. Sometimes, however, as in all the transverse processes of Siren 
(fig. 9, c), except the first one or two, and as in the posterior ones 
of Proteus and the middle ones of Amphiuma (fig. 16), each one, 
though very short, is wide, 7. e. much extended from before backwards. 
Each such transverse process springs generally from about the 
middle of each centrum’s length, but sometimes, as in most posterior 
truuk-vertebree of Siren (figs. 14 & 9) and Amphiuma (figs. 1 & 16), 
mainly from near the anterior end of each vertebra, and sometimes, 
as in the anterior trunk-vertebree of Amphiuma, Menobranchus, and 
Siren (fig. 13), from near the hinder end of each. 
The backward inclination of the distal end of each transverse process 
is sometimes rather more marked at the anterior part of the series, as 
in Siren, Amphiuma, Menopoma, and Cryptobranchus. Each of these 
fully developed transverse processes is more or less excavated by a 
groove or depression on its anterior surface, and another one on its 
posterior face ; and these excavations are often such as to cause more 
or less of a division of the distal part of such transverse process into 
a superior portion and an inferior part. It is also to be observed 
that each transverse process at its point of origin from the vertebra, is 
connected below with the centrum of such vertebra, while above it is 
continuous with its neural arch and more or less distinctly continuous 
with the interzygapophysial ridge. Thus each transverse process 
may be regarded as made up of two parts, each ending distally 
in a more or less distinct process, the upper one of which is called 
the upper or tubercular process *, while the lower one is termed 
the lower or capitular one. Similarly it will be convenient to speak 
of the rib as made up of two portions, a superior tubercular part 
and an inferior or capitular one. When the transverse process is 
nearly cylindrical, as in Salamandra and most forms, these two com- 
ponent parts are of about equal antero-posterior extent ; but some- 
times, as in the middle trank-vertebree of Amphiuma (figs. 4 & 5), 
Proteus, and Siren (fig. 2), the capitular part is much wider from 
before backwards than is the tubercular part. The same is observ- 
able in a less degree in Menobranchus and Aneides. When (as in 
Siren after the first nine vertebre) the tubercular process is also 
wide, and the groove before mentioned almost or entirely confined to 
the front surface, where it is immense, the transverse process assumes 
the form of two triangular plates (of which the upper is the smaller) 
united to the centrum by one margin and to each other by their 
two posterior edges, leaving a space between them which widens as 
they (the plates) diverge forwards (fig. 3, c.7). This space or fossa, 
* By analogy with the condition of higher vertebrates in which the rib has a 
“tubercle” and a “head ” respectively articulating with parts homologous with 
those here described. 
