that the chief peculiarities presented by the cervical vertebrae of this genus are
confined to the united 1st and 2nd cervical vertebrae and to the imperfection of
some of the neural arches. The measurements of united atlas and axis:—
Inohea.
Across transverse processes of atlas . . . . . . . . . . . 4'20
anterior border of occipital facets ................................................ 3'93
Depth through anterior . . . . . . . . . . . . . 1‘62.
Antero-posterior length o f centrum . . . . .• . . ; . . ' . . 1*36
„ breadth of laminse o f neural arch above posterior zygapophyses . . . l'la
Height of neural arch a n ter io rly .................................................................... 1*25
Viewing the remaining vertebrae as a whole, they do not present any very striking
features. The spinous processes of the dorsal region are moderately developed and back-
wardly directed, but in the 1st dorsal, as I have pointed out, the neural laminae are
sometimes not united, and even in the 2nd, 3rd, and 4th dorsal, the laminae of opposite
sides are posteriorly separated from each other by an incision, and this may be traced
more or less to the 8th dorsal. The tips also of the spinous processes of the 4th to the
10th dorsal manifest a tendency to bifurcate. The body of the 1st dorsal is about
one-third thicker than that of the last cervical, and the vertebrae behind it gradually
increase in size to the 10th dorsal, the latter having an antero-posterior thickness of
l"-95, whieh is the maximum length attained by the body of any vertebra.
External to the anterior zygapophysis on the 5th dorsal there are distinct indications,
of a mammillary process, and its presence indicates the vertebra in
which there is the first appearanee of a tendency in the anterior and posterior
zygapophyses to shift their position upwards along the neural laminae to the base
of the spinous processes. On the 7th dorsal the anterior and posterior zygapophyses
have become wholly transferred to the base of the spinous process of that vertebra.
The anterior zygapophyses diminish in length from the 10th dorsal. The transverse
processes of the dorsal vertebrae have the usual Cetacean character.
In the lumbar vertebrae the neural carnal rapidly diminishes in diameter from
(>'•89 to 0"’38, and also in height, the height of the canal in the first of these vertebrae
being 1"-16 and in the last 0"'95. The spinous processes are directed backwards, their
anterior margins being concave and their posterior margins convex.. They increase
in length to the 8th, but diminish in length and in breadth from the 10th dorsal to the
last caudal, with a trace of a spinous process, the diminution in the latter dimension
being very gradual In the 8th lumbar the tip of the spinous process is l"-60
above the level of the posterior ridge from the zygapophysis, and the latter
point is 1"'40 above the body of the vertebra. The processes are relatively consider-
ably shorter than in Phoccena. The anterior zygapophyses retain their conjoint
bifurcate, character as far as the. 9th lumbar, clasping the posterior zygapophyses
of the 8th segment, but in the, 19th lumbar they suddenly become reduced in
dimension to a rounded plate not touching the vertebra in front, of it, and all. trace
of a mammillary process disappears on the last lumbar.
The; transverse, process of the first lumbar is about one-fourth longer than the
transverse process of: the last dbrsal, and is: much more backwardly directed.. The
processes gradually increase in length to. the 5th lumbar, becoming, more and more
outwardly directed until they are nearly at right angles to the long axes of the bodies,
but yet with a slight backward tendency. Measured from the centre of the body
of the 5th vertebra posteriorly to its tip, the length of this process is only slightly
in excess of the interval between the first mentioned point and the apex of the
spinous process, which is exactly the reverse of the proportion between the transverse
and spinous processes of Globicephctlus, from which the skeleton of Orcella is
remarkably different, in such details. In the 5th, 6th, and 7th lumbar vertebrae the
lengths of the transverse processes and their proportions to the spinous processes
are much the same as in the immediately preceding vertebrae, but in the 8th the
transverse process becomes slightly shorter, but hardly perceptibly so. In the 10th
the diminution in length is more visible, and with this diminution the process tends
to curve forwards. Decreasing in length, the processes increase in antero-posterior
breadth towards their tips in the lumbar vertebrae.
In the two sacral Vertebrae there is a considerable alteration in the character of
the transverse processes as compared with the 8th lumbar, hut the transition is
gradual. In the sacral, the process is contracted at its base and expanded towards
its tip, and the forward curve of the external half of the process is more marked
than in the preceding vertebrae. The transverse process is nearly equal to the height
of the spinous process measured from the centre of the body. The height of the
neural canal is kbout one-third, and its greatest breadth is about one-eighth the
height of the neural arch and its process combined.
The four succeeding caudal vertebrae have much the same character as the
sacral vertebrae, but they differ from them and the four preceding lumbar vertebrae
in the greater development of the processes occupying the position of zygapophyses
and in the appearance of a ridge which passes backwards from the front margins of
the latter in the locality of a mammillary process. The length of the spinous and
transverse processes gradually diminishes, and the breadth of the latter increases with
their forward curve, and the spinous processes become nearly vertical.
In the succeeding caudals the bifurcate process in the position of a zygapophysis
is even better marked, as it is traced to the 41st vertebra, in which the height
of the spinous process measured from the middle of the body is less than the length
of the transverse process taken from the same point. In the 40th vertebra, the free
end of the transverse process is obliquely shortened, the direction of the process
being much forwards. These two last-mentioned characters become more pronounced
in the next five vertebrae, associated at the same time with a reduction in
the length of the transverse process which in the 44th vertebra is reduced to a hooklike
process. The spinous process suffers considerable diminution in length with a
gradual downward subsidence, towards the bodies of the vertebrae, of the processes
in the position of the anterior zygapophyses, and the ridge connected with them
becomes more marked as it is traced backwards. In the 46th vertebra the transverse
process becomes reduced to a lateral ridge on the front half of the body, but the
spinous process is well marked, also the neural canal. The former of these processes
disappears on the 47th and the latter on the 51st segment.