made up of fine gritty papillae. Some of these structures also occur on the fauces.
I have never observed them in 0. brevirostris. They occur in a more scattered condition
as far back as the posterior wall of the tube of the larynx. Isolated gritty
papillae are also distributed over the tube of the larynx and the area immediately
posterior to it, and they can be traced some way down the oesophagus.
Pelvic bones and male organ—The crura of the penis (Plate XXVA, fig. 3,
cc, and cc*) are attached by a strong fibrous connection to the pelvic bones
(fig. 3, p and p.* and fig. 4, ap.) which are placed opposite the 15th and 16th lumbar
vertebra; (fig. 3, c, t, sp.)l and the characters of these bones, their position and
variability, are depicted in Plates XXVA, fig. 4, and XLII, fig. 11: The retractor
penis, which is highly contractile, lies between the two crura, and at its origin
is expanded over the strong fibrous band connecting the two pelvio bones (pp.1).
When pulled out it suddenly contracts to half its extended length. The penis
is simple and without lobes, and from the base of the prepuce to the tip measures
three inches in its quiescent state, but from the way the hinder portion of the
organ is doubled on itself, it is evident that when distended with blood it is
capable of considerable elongation, probably reaching nine inohes in length. The
glans or preputial portion is of nearly equal breadth throughout, its transverse
exceeding its dorso-ventral diameter, as it is slightly flattened from above downwards.
Its greatest diameter is about three-quarters of an inch. About three-
quarters of am inch from its extremity it tapers rapidly to a fine point with a slight
intervening swelling, and this portion of the glans with the tip has a remarkable
resemblance to the head and snout of a Trionyx. The orifice of the urethra is
exceedingly small. The terminal inch constitutes the true glans, and it is coloured
like the external skin of the animal, while the portion behind has a pinkish hue.
The dorsal surface, unlike any other Cetacean or mammal that I am acquainted with,
is marked by a mesial ridge, which begins at the base of the prepuce and extends to
the tip of the organ, interrupting the somewhat concentric wavy transverse folds into
which this part of the organ is thrown when at rest and which relate to extension.
At the base of this long raphe on either side there is a rather large papilla marked
at its tip by a patulous orifice, the opening of a gland. I am unabie to say whether
such a structure exists in the allied species O. Iremrostris, as I have had the
opportunity to examine only one badly preserved male.
Shull.—1The skull (Plate XLII, figs. 1, 2, and 3) of the purely fluviatile dolphin
of the Irawady has so very strong a likeness to that of the round-headed dolphin
of the Bay of Bengal and its estuaries, first described by Professor Owen as
Phoeeena brevirostris, 3 that were the skulls the only materials for determining
the species, considerable dubiety would inevitably be experienced in deciding
on their specific distinctness. But when the animals are studied as a whole the
only reliable method—other characters gradually unfold themselves, which, when
1 The pelvic bones of this species a n subject to considerable variation. See Plate X X \ fig. 4, and Plate XLII,
fig. II.
2 Trans. Zool. Soc., vol. v i , p. 24, pi. six, figs. 1 to 3.
duly weighed in conjunction with the perhaps otherwise unimportant differences
manifested by the skulls, lead to the conclusion that the modification of structure
has proceeded to that degree that in its totality it confers a specific character
to this form—a result which was to he looked for in view of its peculiar habits
of life.
The first point of difference between these skulls, in fully adult individuals,
which strikes the observer is the more flattened occipital region of O. jlummalis,
directed downwards and backwards, whilst in 0. brevirostris it arches backwards,
downwards, and slightly forwards. Another difference consists^ in the more depressed
character of the super-occipital and interparietal region of the skull of
Orcella jlummalis, an area which is considerably arched in O. brevirostris. This
feature, however, is more pronounced in the skull figured by Owen than in fully
adult skulls, and is doubtless a character of immaturity. The next distinctive
feature is the shorter and broader snout of the former as compared with the latter,
the specific name of which is inappropriate, seeing that it corresponds to no external
character, and might therefore mislead to the supposition that the dolphin had
a projecting snout in the flesh, of which there is no trace whatever. In Orcella
brevirostris the snout tapers gradually to a point from a slight lateral bulging
in the maxillaries, beginning in the adult skull about 0*88 inch anterior to the
preorbital notch, but in O. jlummalis the lateral margin tapers to a point much
more gradually than in 0. brevirostris. The maxillaries, too, in the snout of
the former, ore comparatively flat, and do not shelve downwards on the sides
as in the latter species. In 0. brevirostris the premaxillaries contract opposite to
the preorbital notch, while no such marked contraction occurs in O. jlummalis,
in which these bones, instead of varying in their breadth, as in the former species,
preserve a nearly uniform width throughout. The intermaxillary space is also
much wider in 0. jlummalis than in O. brevirostris, and the nasals are more
anterior and lower in the former than in the latter. Viewing the skulls in front,
the breadth, on a level with the posterior extremities of the premaxillaries, is
proportionally slightly greater in O. jluminalis than in O. brevirostris.
Turning to the base of the skull (fig. 3), we find that the relative size and form
of the palatines are quite different in-the two species. In O. brevirostris these bones,
as figured in Owen’s drawing of a rather young skull, form a very small portion,
viz., 0T6, of the posterior extremity of the mesial line of the palate, and in other
skulls of this species before me they form even a still smaller surface. In an
adolescent skull they are 016, but they do not form a suture, while in an adult
cranium they are nearly on a level with the posterior extremity of the palatine
surface of the maxillaries. In 0. jluminalis, on the other hand, the sutures of the
palatine, in an adolescent skull, are well defined, and the palatine is 0-52 inch in
length, while in the adult it is 0*60 long and retains the same character. As is seen
in Owen’s figure of O. brevirostris, the tendency of the palatines is to contract in
the middle towards the mesial line, and in two skulls of this species, young and
adolescent, the contraction has been carried to complete division, while in the adult