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Show 1870.] AXIAL SKELETON OF THE URODELA. 267 summit, and in the fresh state has evidently a cartilaginous continuation (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 vertebrae, but the posterior processes abort at about the fifth or sixth caudal vertebra in Menobranchus, and at about the seventh in Cryptobranchus. 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 cristatus, 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 vertebrae near the end of the tail. A longitudinal ridge (figs. 3, 7, 8, 17 0, more or less marked, Dorsal view of last trunk- and anterior caudal vertebra? of Amphiuma. Hy. Hypapophysis. i. 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), especially in the latter. In other forms it is but little so in the trunk-vertebrae, though often becoming prominent in the caudal ones, as notably in Chioglossa. Fig. 8. Lateral view of anterior caudal last trunk-vertebra? of Siren (No. 576 B in Museum of College of Surgeons). c. Capitular process, t. Tubercular process, i. Interzygapophysial ridge. TRANSVERSE PROCESSES. With the exception of the cervical vertebra and of all the caudal vertebrae 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 |