Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/64

 6O THE EXTINCT BATRACHIA, REPTILIA tebra and the head of the femur; the third a nearly perfect vertebra and diapophysis of another, with dermal bones; the fourth the greater part of the femur, with fibula and dermal bones; fifth, ribs and dermal bones, with pelvis. Seven vertebrce present centra, and are more or less nearly perfect. There are probably uo cervieats, but there are three forms of diapophyses which indicate different positions in the vertebral colimm. That which I suppose to represent the most anterior, has a short, wide diapophysis with tnbercular articular sur-face, and a short knob with capitular articulation at the base of the anterior aspect of the neurapophysis, with its su-perior margin on the plane of the diapophysis. In the next, the diapophysis is short, wide, and closely connected at the base with a eapitular articular tubercle, for the rib, the extremity of the diapophysis furnishing the tubercular surface. In the first of these the diapophysis is as long as the elevation of the anterior zygapophysis above the cen-trum, and the capitular knob measures the middle of the latter space with its superior margin, being in the plane of the diapophysis. In three others the elevated position of the eapitular articulation is visible. The second form of diapophysis is seen in a nearly perfect vertebra in immediate connection with that first described above, but probably in abnormal relation. The process is narrower, but flat. and without capitular process at base, nor is there any eap-•ular articulation on the tantrum. Its position is much lower than in those just described, being opposite to the middle of the centrum. Its extremities are imperfect, probably broken oft'. I suspect that their condition is indicated by an isolated diapophysis, which is accompanied by tubercular articular face at a distance of 18 lines from its extrem-ity, and probably at some distance from its base, which is. however, lost. The third type of diapophysis is seen in two examples; one, in normal relation to its centrum, etc. This is quite slender awl elongate, compressed at base, and cylindric throughout most of the length. On the posterior face of the extremity is a slightly concave articular face; the extremity proper appears also to have borne the tubercular face. That these are the combined tubercular and ar-ticular facets is rendered altogether probable by their wider separation on the second example of this form. This is an isolated diapophysis, of slender cylindric form, which, at a distance of an inch from the extremity dilates into a right-angled flat process, whose distal side bears a narrow eapitular articular face. The extremity is subcylindric, hearing the tubercular facet. This arrangement of the vertebrae is confirmed by the arrangement seen in other species, where vertebra similar to those first described are evidently dorsal. It is probable from the above, that the capitular articulation rises from the centrum very soon in this type, as in the Crocodilia, perhaps very few dorsals retaining it on that portion; and differing from the Dinosaurian type, where this facet is on the margins of the centra and not elevated on a pectic& This form differs from the Crocodiles in the narrowing and final cylindric form, as well as descent on the centrum of those diapophyses on which the two facets approach and unite. One objection to the position assigned to the last form of vertebra, is the fact that the only one with perfect cen-trum presents an oblique truncation on the posterior margin on each side, which looks much like a capitular articular face. There is a precisely similar vertebra in the Museum of the Acad. Natl. Sciences, from Chatham Co., N. Ca., which is ascribed to the B. earoliucnsis. Their surface is concave in this specimen, but seems too large for the head of a rib. In both, the vertical diameter is oue-half the transverse width of the articular face of the centrum. I can-not assign the place or use of this facet with certainty, but the following light is thrown upon the point by another specimen in the Museum Academy, also from Chatham Co., N. Ca., presented by Prof. Emmons. It consists of five consecutive yertehrte on a block of coal slate, of which the anterior two present the capitular tubercle elevated to the base of the short fiat diapophysis, without being confluent with it in the first, but closely united to, and of equal length with the shortened second. On the third, the rib-diapophysis becomes abruptly very much wider, and occupies a position a little lower down on the centrum. The diapophysis is preserved on oue side of the block. It is flat, a little narrowed beyond the middle, then dilated, and with an open margination opening pos-teriorly and outwards, at the distal extremity. With the extremity it bears a narrow articular surface. These I sus-pect to represent capitular and tubercular articulations. The fourth and fifth vertebra bear each, a greatly dilated and thiekened diapophysis, which I have little doubt represent the sacral supports of the ilium. Their expanded bases are somewhat lower in position than the diapophyses of the vertebra in advance, and they occupy a broad arti-cular face of their proper vertebra, and a distinct facet of that preceding, leaving an artieular face on its posterior margin. I suppose the peculiar vertebra already alluded to iu the B. lepturus and specimen from North Carolina, are, therefore, the last lutubars.