"The general form of the vertebræ is cylindrical, but their sides are compressed obliquely, which gives to the contour of the centra a subhexagonal appearance. They are much flattened in the direction of the antero-posterior diameter, which has to the transverse diameter the proportion of 1 to 3. Both the articular terminal facets are deeply and equally concave; but from the center to the margin the surfaces are convex, and this convexity is greatest near the center. * * * The cavities for the reception of the intervertebral matter begin immediately from the margin, and are considerably deeper than the corresponding parts of the _Ichthyosaurus_, indicating a greater degree of flexibility in the vertebral column. The margins of the vertebra; are somewhat raised, as if they had yielded to a forcible compression applied longitudinally; and hence the lateral surfaces of the centers are concave in an antero-posterior direction. This concavity is greater in the upper half of the vertebra and was undoubtedly more marked originally than at present, since the appearance of the margins indicates considerable abrasion. The non-articular surfaces of the centra are smooth and regular; and the external fibres of the osseous tissue are singularly reticulated. [Illustration: Fig. 41. Nova Scotian Amphibia. A. Oblique lateral view of vertebra: of _Eosaurus acadianus_ Marsh, _a_, pits for articulation of neuropophyses; _b_, rudimentary transverse process on right lateral surface of centrum. B. Oblique view of vertebræ, _a_, pits for articulation of neuropophyses; _b_, rudimentary process on lateral surface. C. Posterior view of nearly perfect centrum. D. Transverse section of same vertebra, showing deep concavities of articular terminal facets. E and F. Microscopic sections near surface, showing lacunæ arranged around an Haversian canal. Magnified 200 diameters. (All figures after Marsh. × 0.75.) ]