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Show -74 MR. ST. GEORGE MIVART ON THE [Api*. 28, HYPAPOPHYSES. That system of inferior arches, or parts of such, which is in more immediate relation with the great dorsal artery attains in the Urodela 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 Siren and Amphiuma (fig. 13), and more Fig. 13. Under view of first four vertebra? of Siren (No. 576 B in Museum of College of Surgeons). Hy. Hypapophysis.* or less in Menobranchus (beginning with the second or third vertebra), 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 forwards, 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 surface of all the praecaudal vertebrae, except the first and the last one or two. This ridge is more or less divided (fig. 14) medianly into Fig. 14. Under view of transitional vertebra? (from trunk to tail) of Siren (No. 576 B in Museum of College of Surgeons). Hy. Hypapophysis. 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 Menobranchus. 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 apparent 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 side, although the transverse process is furnished with a distinct though small rib. |