Dia MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
There are broad flange-like lateral plates or processes, perforate, as usual, for 
arterial canals. The azis develops a stout, erect spine, overtopping that of 
any other cervical excepting the 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 
the 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 laminze. The delicate 
“transverse” processes are largely fenestrate with the circular vertebrarterial 
foramina. The stzth 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. Its 
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- 
“dorsal” in character, in (a) 
more, and chiefly, this last cervical vertebra is 
possessing no vertebrarterial canal, and (d) in bearing on the posterior border 
of its centrum a demi-facet which takes equal share with that of the 1st dorsal 
in the articulation of the 1st rib. 
Of the thirteen dorsals, the 1st is mainly discriminated from the last 
cervical by the presence on the apex of the transverse process of a cupped 
facet for the articulation of the tubercle of the 1st rib; for we have just seen 
how closely the last cervical simulates characters of a dorsal, even to taking 
its share in bearing a rib. Its spine is, however, abruptly still longer; its 
transverse process is altogether stouter (besides bearing a facet); and its 
body is narrower, longer, and more nearly cylindrical. The last (13th) dorsal 
is distinguished from the 1st lumbar by presence of the facet for the last rib, 
and by total lack of a small anterior prolongation or point of the “transverse” 
process, which is readily recognizable upon the anterior lumbar, and becomes 
very conspicuous on succeeding bones of that series. The centra of the dor- 
sals grow longer, narrower, and more protuberant inferiorly from the 1st to 
