but separated from each other by a groove, which can be detected in a similar
position as far back as the nineteenth caudal vertebra.
The dorsal fin lies over the eighth lumbar and first caudal vertebræ, its apex
being between the spinous processes of these vertebræ.
Bibs (Plate XLI, fig. 16) vary in number from ten to eleven. There are
one prestemal and three mesosternai. The first two are thick and nearly cylindrical,
whilst the third is slightly compressed from without inwards, a character
which becomes more intensified in the succeeding ribs, especially from the fourth
to the eighth, in which the shafts have considerable antero-posterior expansion,
though less marked in the remaining two. In the first, the part intervening
between the tubercle and angle is compressed from before backwards, but with
the tubercular portion much more .strongly developed than in dolphins generally,
and the neck, instead of being merely a flattened prolongation of the shaft, is
narrow, .compressed, and angular, with three surfaces, and diminishing in thickness
from the base of the tubercle to the head. The outer surface of the angle
is marked by a rough surface for muscular attachments. In the second rib, the
anterior becomes the external surface in the lower third, as the shaft is twisted
on itself, and the external surface between this and below the angle is almost ridge-
like, the posterior surface being round. Erom the angle to the head, the rib is
much antero-posteriorly compressed, and the outer aspect for an inch and a half
below the angle is produced outwards into a prominent curved muscular ridge
directed backwards and downwards, being continuous below with the rather sharp
external border of the rib, while above, it is prolonged putwards and forwards
beyond the angle as a laminar triangular process. This ridge can be traced as far
back as the seventh rib, but gradually distally receding, its place in the eighth and
ninth ribs being taken by a flattened smooth surface on the posterior border, but it
re-appears in the ninth and tenth. The surfaces of the second rib are the same as in
the first. The neck is short, there being only 0*42 inch between the tubercular and
capitular surfaces. A well-marked process occurs on the lower border of the neck
immediately external to the head ; a rudiment of it may be detected in the first rib,
whereas it is strongly developed in the third, but almost lost in the fourth rib. In the
third and succeeding ribs to the eighth, the shafts are externally flattened, but strong
and thick, the neck gradually diminishing in length till the tubercular portion and
head are merged in one in the sixth and following ribs. The angle is very well marked
in the third rib, as the triangular process is strongly developed, but in the following
ribs it forms a more and more obtuse angle with the shaft. Thé tenth has occasionally
a supplementary articular process on the posterior margin of the angle by-
which it is in contact with the transverse process of the eleventh vertebra (Pl. XEI,
fig. 15) to which it is bound by strong ligamentary bands. An eleventh rib is occasionally
superadded, articulated to the eleventh and twelfth transverse process, and
sometimes applied to the rough surface on the posterior border or angle of the
tenth rib, which otherwise, so to speak, would have been itself applied to the
eleventh transverse process. In some cases there are ten ribs on one side and eleven
on the other, following the foregoing arrangement.
In a newly-born individual before me, there are only ten ribs on either side, and
neither of its terminal ribs touches the eleventh transverse process, but in a foetal
skeleton both of these are closely bound down to the eleventh process, from which a
rather long piece of cartilage projects outwards and backwards.
Eour pairs of ribs are articulated to the sternum, cartilaginous in the young
but ossified in the adult condition, separated, however, from the vertebral ribs by an
intermediate piece or- cartilage, as already stated.
The scapula has its posterior border on a line with the posterior margin of
the BiTrth rib, its hinder angle being on a level with the middle of the rib. The
anterior angle of the scapula (process) is on a line with the anterior margin of the
arch of the fourth cervical vertebrae, and its superior anterior angle is opposite to
the arch of the fifth cervical, and the highest point of the bone is on a level with the
spinous process of the first dorsal in a young individual.
The diaphragm is attached on a line with the inferior border of the sternum,
running along the inferior margin of the cartilage of the fourth rib, from thence
on to the apices consecutively of the free osseous ends of the fifth to the eighth
rib inclusive. I t then passes across the ninth rib a short distance above its apex, and
from that crosses the tenth rib obliquely a still further distance above its apex, passing
transversely across from side to side in an arch between the tenth and eleventh
dorsal vertebrae.
Sternum (PI. XXXIX, figs. 5, 6 & 7).—The prestemum is large and broad
generally more or less notched in front, with convergent or lateral borders and a
transversely broad, abruptly truncated posterior extremity; it has a general resemblance
to the prestemum of Bhyseter macrocephalus, if the fontanelle and mesial
suture of that presternum were filled up. I t is subject, however, to great variations
in its anterior border, depending on the degree to which the cartilaginous interval
has filled up. In adolescents, it frequently forms a deep notch anteriorly. There
is no trace of the process which in the dolphins and porpoises occurs behind the
articulation for the first rib. The breadth of the prestemum posteriorly equals
one-half of its greatest breadth between the articulation of the two first ribs, and
the .mesial length is one and a half as long as the posterior breadth. I t is slightly
concave on its inner aspect and convex externally, and in an adult female there are
distinct indications on the same aspect of the mesial sutural line of the two original
elements. The facet for the first rib is borne on a slight projection of the anterior
angles of the bone and looks backwards and outwards. The position of this rib,
however, would appear to be variable, because in a young skeleton presented to the
Medical College, Calcutta, by the late Dr. Ealconer, the first rib on the right side is
situated on the lateral border of the prestemum, if anything, below its middle, far
remote from the anterior angle, and on the left side it is also removed from the usual
position, but anterior to the middle of the lateral border. There can be no error in
this observation because the skeleton is a natural one, none of the attachments of the
u 3