. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. 572 MONOGRAPHS OF KOBTH AMERICAN BOD&NTIA. f^sV' i. There are broad flange-like lateral plates or processes, perforate, as usual, for arterial canals. The axis d'.s Rlops a stout, erect spine, overtopping that of any other cervical excepting tiie 7th; it is compressed, prominently and sharply ridged anteriorly; ridged, but less sharply and prominently, behind; and its apex is tuberculate. The centrum is small and much flattened; the odontoid is well marked, and all the front of the body of
. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. 572 MONOGRAPHS OF KOBTH AMERICAN BOD&NTIA. f^sV' i. There are broad flange-like lateral plates or processes, perforate, as usual, for arterial canals. The axis d'.s Rlops a stout, erect spine, overtopping that of any other cervical excepting tiie 7th; it is compressed, prominently and sharply ridged anteriorly; ridged, but less sharply and prominently, behind; and its apex is tuberculate. The centrum is small and much flattened; the odontoid is well marked, and all the front of the body of the bone, including tlie inferior aspect of the odontoid, presents a continuous articular surface for the atlas. The articular facets for the 3d cervical scarcely represent processes, being simply borne upon the bases of the neural laminee. The delicate "transverse" processes are largely fenestrate with the circular vertebrarterial foramina. The aixik cervical is peculiar in the points mentioned above. The seventh cervical, as in human anatomy, is a "vertebra prominens", its spine being abruptly longer than that of the preceding bone; it is more than half as long as that of the first dorsal, which, in general appearance, it resembles closely. In other points, this last cervical foreshadows the dorsal series, lis transverse process stands straight out from the axis of the column, like that of the 6th cervical, instead of obliquely backward, as in the rest of the cer- vical series, and is notably longer than any antecedent one. The centrum is abruptly narrower than the body of the 6th cervical, beginning that com- pression and cylindricity which marks the dorsal and lumbar series. Further- more, and chiefly, this lost cervical vertebra is "dorsal" in character, in (a) possessing no vertebrarterial canal, and (6) in bearing on the posterior border of its centrum a demi-facet which takes equal share with that of the Ist dorsal in the articulation of
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