266 MR. ST. GEORGE MIVART ON THE [Apr. 28, 
these conspicuous productions of the neural arch* ascend almost 
vertically, as they do in some of the posterior caudal vertebrae of 
Siren (fig. 8), and tend to do in those of Amphiuma. The summit 
of the neural arch in Urodela is never produced into a long bony 
Fig. 5. 

Dorsal view of 23rd, 24th, 25th, and 26th vertebree of Amphiuma. 
H. Hyperapophysis. c. Capitular process. 7. Tubercular process. 
pointed process, as it is in so many higher vertebrata ; but sometimes 
the middle of its hinder margin projects slightly backwards, as in 
Menobranchus ; and sometimes, as in Menopoma, Cryptobranchus, 
and Menobranchus (fig. 10), the posterior part of the caudal neural 
arches are produced into long processes inclined obliquely backwards 
over the succeeding vertebree; but they are hollow and open at the 
summit, and are no doubt continued in cartilage. Sometimes again 
the posterior part of each neural arch, whether of the trunk or of 
the tail, is marked by a vacuity, pit, or depression, as if for the im- 
plantation of the end of a cartilaginous rod or spinous process ; this 
is found in Cryptobranchus aud Menopoma. In Amblystoma each 
neural arch of the posterior trunk-vertebree possesses two such pits 
placed side by side in the same transverse horizontal line as if for two 
cartilaginous neural spines ; and the same structure obtains through- 
out the caudal vertebree. In the Axolotl the trunk neural arches 

Dorsal view of three caudal vertebree (sixth to eighth postsacral) of Axolotl, 
from specimen No. 582c in Museum of College of Surgeons. 
have, from before backwards, successively longer and longer neural 
spines; but each one has a concave depression at its tip, as if it were 
continued in cartilage. The caudal vertebre in the same form, from 
the fourth backwards, have each bifold neural spines, as in the trunk- 
and all caudal vertebrae of Amblystoma; and each is concave at its 
* These parts appear to correspond with those mammalian processes for 
which I have proposed the term hyperapophyses (P. Z, S, 1865, p. 576), and the 
presence of which often serves as a good osteological character for zoological 
groups. See Cambridge Journal of Anatomy and Physiology, vol. 11. pp. 143-154. 
