278 ON THE AXIAL SKELETON OF THE URODELA. [Apr. 28, 
DorsaL VERTEBRE. 
The vertebree interposed between the cervical vertebra and the 
sacrum vary in number from twelve (Taricha) to sixty-three (Am- 
phiuma). They are always the largest vertebrae of any one indivi- 
dual axial skeleton. 
All have neural arches and anterior and posterior zygapophyses. 
Except in Siren, Proteus, and Amphiuma, all these vertebre sup- 
port a transverse process and a rib on each side of the body. 
Some few forms have small hypapophysial processes (e. g. Spe- 
lerpes), or single median ridges, or such ridge more or less cleft lon- 
gitudinally. The various parts and processes of the vertebree have 
been already described. 
SacrAL VERTEBRA. 
Never more than one vertebra is normally connected with the 
hip-girdle; but not very unfrequently the ilium of one side is 
connected with the transverse process of one vertebra, while the 
other ilium attaches itself to another vertebra. The transverse 
process of the sacral vertebra is generally stout, as also the an- 
nexed rib. The latter is especially predominant, as compared with 
the ribs in advance of it, in Avolotl. In Proteus and Amphiuma 
this vertebra is without arib. In no genus does it develope a hypa- 
pophysial process. 
CaupAL VERTEBRE. 
These vertebrae always decrease in size successively from before 
backwards ; the last ones are often merely little bony ossicles without 
processes of any kind. The number.of caudal vertebre varies from 
22 in Cryptobranchus japonicus *, and sometimes in Menobranchus, 
to about 43 in Amphiuma or 53 in Siren. All except the more pos- 
terior ones are provided with neural arches and, with the exception 
of the first one or two, with hypapophyses. These latter unite to 
form hypaxial arches in all the species except Siren. Transverse 
processes are sometimes to be traced for a great distance along the 
tail, as in Stren, Chioglossa, &ec. Sometimes, as in Cryptobranchus 
and Menopoma, every trace of them disappears at the seventh or eighth 
caudal vertebra. Sometimes both tubercular and capitular processes 
stand out distinctly one above another, as occasionally in the fourth 
vertebra of Menobranchus (fig. 10, c, ¢). Small ribs are sometimes 
attached to the first caudal vertebra, and also to the one or two 
following ones, as in Menopoma and Cryptobranchus. 
Anterior and posterior zygapophyses are always developed in the 
anterior caudals, and continue backwards for a variable, sometimes 
(e. g. in Amphiuma) for a great extent. But it is here unnecessary 
to recapitulate details as to the various parts and processes of these 
vertebrae, which have already been given under the various preceding 
headings. 
* In Brit. Mus. 
