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.)
"The neuropophyses are not anchylosed to the centrum, as in the mammalia, nor connected to it by sutures, as in the crocodiles; but their union with the vertebra is indicated by two pits, which served for their articulating surfaces. These depressions are situated on the superior surface of the centrum intermediate between the anterior and posterior margins of the extremities. They are circular in form and sink directly into the body of the vertebra; instead of being elongated longitudinally and raised by ridges, as in Ichthyosaurus. The pits are about a line in depth, and in the more perfect of the fossils are not in their original position. The floor of the spinal canal is narrow, being but 5 lines in breadth. A rudimentary transverse process, or exogenous tubercle, is sent off from each lateral surface of the centrum, at points equidistant from the extremities of the vertical diameter. Their position is near the margin of the anterior articular surface, and the edges of these p arapophyses make the transverse diameter of this extremity somewhat greater than that of the corresponding posterior facet."
| Measurements of the More Perfect Vertebra of Eosaurus acadianus (after Marsh). | |
| mm. | |
| Transverse diameter of centrum on anterior surface | 59 |
| Same on posterior surface | 57 |
| Same including the parapophyses | 63 |
| Vertical diameter of anterior surface | 54 |
| Anteroposterior diameter on superior surface | 21 |
| Same on inferior surface | 19 |
| Same between centers of articular facets | 2.5 |
| Length of pits for articulation of neural arch | 7 |
| Breadth of same | 7 |
| Depth of same | 2 |
| Distance between centers of same | 11 |
| Same at centers of parapophyses | 36 |
Collected by O. C. Marsh at the South Joggins, Nova Scotia.