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Show 276 MR. ST. GEORGE MIVART ON THE [Apr. 28, into each arm of the notch (fig. 16), ending in two strongly projecting processes, like the similarly conspicuous productions of the caudal neural arches before described. These processes are also especially marked in Proteus, Amphiuma (fig. 17), and Spelerpes rubra, and more or less so in Triton palmatus, Pleurodeles waltlii, &c. In Spelerpes rubra these prominences descend almost vertically, corresponding with the position of their vertical homologues above. The median inferior crest is often more vertically extended than is the corresponding neural one, as is the case in the species last mentioned (except Amphiuma, where there is hardly any median inferior crest, and then only in the very posterior caudals) and in Aneides. These backwardly projecting lateral processes extend over the anterior part of the hypaxial arch next behind, and thus somewhat simulate posterior zygapophyses ; but these arches have no true articular processes, as is well seen in such forms as Cryptobranchus, Menopoma, and Amphiuma, where the contrast is marked. Very generally, as in Triton, Amphiuma (fig. 17), Pleurodeles, and, above all, in Last trunk- and anterior caudal vertebra? of Amphiuma (No. 5 7 9 A in College of Surgeons' Museum). H. Hyperapophysis. Hy. Hypapophysis. i. Interzygapophysial ridge. Chioglossa, an oblique ridge extends backwards and downwards from the anterior point of attachment of each half of the hypaxial arch to the backwardly projecting inferior process of the same side. These ridges appear to be the only parts of the hypapophyses that are left in those forms in which the hypapophysial arches are very narrow. They somewhat resemble the interzygapophysial ridges of the caudal neural arches, but are more oblique in direction. THE CERVICAL VERTEBRA. The vertebra which comes first and articulates in front with the skull differs importantly from all the vertebrae which succeed it. Like the others, it constantly presents a centrum which is concave behind, and from which a continuous, ascending neural arch is developed. But not only are there no hypapophyses, but transverse processes are completely absent, except in Siren (fig. 18), Proteus, and Menobranchus ; and in these genera they are quite rudimentary, while the vertebra is invariably destitute of any costal appendage or rib. But it is the anterior face of the vertebra which is most remarkable. This presents on each side (at the junction of one half |