274 MR. ST. GEORGE MIVART ON THE [Apr. 28, 
HypapopHyseEs. 
That system of inferior arches, or parts of such, which is in more 
immediate relation with the great dorsal artery attains in the Uro- 
dela its full development only in the caudal region, where it appears 
as the hypapophyses and hypapophysial arches. In the trunk the 
most anterior indication of this system of parts is found (1) in the 
anterior trunk vertebrae of Siven and Amphiuma (fig. 13), and more 

Under view of first four vertebra of Siren (No. 5768 in Museum of College of 
Surgeons). 
Hy. Hypapophysis. 
or less in Menobranchus (beginning with the second or third ver- 
tebra), where there is a median antero-posteriorly extended subcentral 
crest, and (2) in certain small bifold processes found in Amphiuma 
(fig. 16) and Spelerpes rubra. These processes may project for- 
wards, as in the first-named genus, from the anterior margin of the 
under-surface of each centrum, except the first three, close to the 
anterior end of the hypapophysial ridge; or, as in Spelerpes rubra, 
they may project backwards from the hinder part of the under sur- 
face of all the praecaudal vertebrae, except the first and the last one 
ortwo. This ridge is more or less divided (fig. 14) medianly into 

Under view of transitional vertebrae (from trunk to tail) of Stren (No. 576 8B in 
Museum of College of Surgeons). 
Hy. Wypapophysis. 
two in that vertebra of Siren which precedes the first one. provided 
with conspicuous hypapophyses, and also in the second vertebra, and 
in the second and third of MWenobranchus. The first caudal vertebra 
is always destitute of any hypapophysis*; and very often the second 
* In a skeleton of Cryptobranchus japonicus in the British Museum the ap- 
parent first caudal is really the second one, the true first caudal has coalesced with 
the sacral vertebra. This really second caudal has a long hypapophysis on one 
ane although the transverse process is furnished with a distinct though 
small rib. : 
