1870.] AXIAL SKELETON OF THE URODELA. 267 
summit, and in the fresh state has evidently a cartilaginous conti- 
nuation (fig. 6). Rarely (as sometimes in Menobranchus) the neural 
arches, towards the end of the tail, each develope two neural spines, 
one in front of the other. 
As has been said, almost every neural arch has four zygapophyses ; 
but the-cervical vertebra has only the two posterior ones. In the tail 
these processes are all developed on the anterior caudal vertebre, 
but the posterior processes abort at about the fifth or sixth caudal 
vertebra in Menobranchus, and at about the seventh in Cryptobran- 
chus. In other forms, however, they extend far back—e. g. to the 
last vertebra but four in Aneides, to the last but five in Triton cris- 
tatus, and to the last but nine in Siren. The anterior zygapophyses 
continue to be developed for a longer distance, being traceable in 
Aneides to the last vertebra but four, and in Cryptobranchus to the 
last but three. In Amphiuma both continue to the very small verte- 
bree near the end of the tail. 
A longitudinal ridge (figs. 3, 7, 8, 177), more or less marked, 

Dorsal view of last trunk- and anterior caudal vertebrae of Amphiuma. 
Hy. Hypapophysis. 7. Interzygapophysial ridge. 
generally extends along each side of each neural arch between the 
two zygapophyses of the same side. This interzygapophysial ridge 
is most marked in Amphiuma and Siren (fig. 17 and fig. 3), espe- 
cially in the latter. In other forms it is but little so in the trunk- 
vertebra, though often becoming prominent in the caudal ones, as 
notably in Chioglossa. 

Lateral view of anterior caudal last trunk-vertebrz of Siren (No. 5768 in 
Museum of College of Surgeons). 
¢e. Capitular process. ¢. Tubercular process. 7. Interzygapophysial ridge. 
TRANSVERSE PROCESSES. 
With the exception of the cervical vertebra and of all the caudal 
vertebree except the first few, each centrum gives out on each side a 
large and conspicuous transverse process. More or less completely 
rudimentary transverse processes are to be traced throughout the 
