TANYSTROPHEUS.
Sp. Tanystrophceus conspicuus, H. von Meyer.—Certain long, slender, hollow bones (fig. 70, A), from the German muschel kalk, were referred by Count Miinster to the class .Reptilia, under the name of Macroscelosaurus, under the impression that they were bones of the limbs. H. von Meyer subsequently, in more perfect specimens, observing that each slightly ex panded extremity of the long bone was terminated by a sym metrical oval concave articular surface, surmounted by a pair of symmetrical lateral incurved plates, resembling confluent neurapophyses, with articular surfaces, and with their times confluent bases arching over a neural canal (as in figure s, in cut 70), recognized their vertebral character ; and, adopt ing the determination of their reptilian nature, but repudiating the idea of their being limb-bones, he discarded Miinster's name, and substituted for it that of Tanystropluzu,s,* indicative of their peculiar proportions as vertebrae. Although the articular ends are for the most part symmetrical, the long intervening body is not so. It is subcompressed, usually broader and flatter below than above ; sometimes more flat tened on one side than on the other, giving an irregular, verti cally oval, or triangular cross section. A low median ridge is not uncommon on the lower surface towards the ends of the vertebra ; and similar less regular ridges project from the sides of the otherwise smooth outer surface. The centrum is excavated by a canal, resembling a medullary one, but more probably filled, in the recent state, as in the long caudal style of the frog, with unossified cartilage. The walls of this cavity are compact, and in thickness about one-sixth of the diameter of the bone. The terminal neural arches support each a low median ridge or rudimental spine, which soon subsides. The trace of neural canal in like manner disappears, or is continued by two distinct slender canals, which traverse for a certain extent the substance of the thicker upper wall of the cavity of the vertebral body. A single large vascular canal opens on
the wider surface midway between the two ends of the body.
There is no trace of transverse processes, rib-surfaces, or ham apophyses ; this, and the absence of the continuous neural canal, indicate these singular vertebra to belong to the tail. From the long caudo-vertebral style of anourous Batrachia the vertebra of Tanystrophmus differ in having distinct articular surfaces at both ends. The difference of shape and size in the few that have been found also indicates that there were more than two such vertebra in the tail of the extraordinary animal to which they have belonged. Caudal vertebra of the normal proportions and structure, from muschelkalk of the same localities with Tanystrophceus have been referred to Nothosaurus. It is possible, however, that one or other of the remarkable genera—Simosaurus, Plaeodus, e.g.—may have possessed the peculiar structure in the tail, or some part of it, which the tanystrophaan vertebra indicate. The first four vertebra of the neck or trunk of the Fistularia tabaccaria are those which most resemble in their proportions the vertebra above described ; but none of the fistularian vertebra have the articular concavity and the zygapophyses at both ends ; the first presents them at the fore end, and the last at the hind end, and the modifications of both these finished articular ends pretty closely correspond with those of Tanystrophceus ; but the second and third vertebra of Fistularia are united with the first and fourth by sutural surfaces with deeply-inter locking pointed processes.