essentially departed from, although slight variety obtains. Among the JDelphmidce
and Globicephalidae, with a transverse outer slit, a pair of oval pads rest against the
hinder wall, and a small cartilage laterally approximates. The vertical passage
descending to the two inner narial orifices sends forwards along the premaxillaries
either a single one or a pair of elongated sacs. These thus bend round deeply below
the facial blubber mass. Erom the spiracular cavity higher up, in some instances
very superficial, a large thin-walled sac diverges outwards on either side. By an
opening close by each of the latter, a narrow, often cord-like sac or tubular canal winds
backwards and inwards, or sometimes even has a twist forwards. Thus, there are three
pairs of sacs, differing in position and shape, all commumcating With the spiracular
cavity : a pair of pads or fibroid eminences, and a pair of rudimentary nasal cartilages,
besides a medial septal cartilage.
Now, the same structures are obvious in Platanista. The longitudinal direction
of the spout-hole produces therewith a very obliquely shelving anterior wall, and
thus the boss roofing the elongated premaxillary sac appears to jut more upwards
and backwards than in those Cetacea with a cross blow-hole. This boss, or anterior
cushion, consists of very firm fibrous tissue, intermingled deeply with fleshy fibres,
forming a premaxillary muscle. The latter again in front commingles with coarser
reticulate fibroid tissue, between the meshes of which oily blubber is retained. Thus,
the cupular eminence of the face, at the sides supported by the porous maxillary
crest plates or arches, is composed of coarsely reticulate glistening fibroid tissue,
with oily matter distributed in it. I t is much firmer than in those Whales in which
it assumes the constitution of true blubber. Below the mass in question is the premaxillary
sac {wood-cut, Eig. 15,1); trending forwards, and connected therewith is a
small outer recess. This latter (II), though much more deeply situated than in the
Dolphins and Porpoises, evidently corresponds to their superficial lateral sac. Just
behind and towards the inside comer of the bony narial aperture a small opening
leads into a diminutive passage (III) curving outwards, and round a pad and gristle
presently to be mentioned. The said pad (¡p) is a nodular mass of solid fibrous
tissue, overhanging the nasal passage. Immediately outside it, starting apparently
from the frontonasal region, and following the course of the upper premaxillary
process is a crescentic strip of cartilage {ca). This is externally convex and internally
concave, prominent behind and shooting downwards and forwards, outside the
anterior boss already spoken of. The passage to the nares lying between them, but
outside the cartilage, is a shallow crescentic depression subsidiary to the narial
channel.
The cartilage is covered by fibrous tissue, and muscular fibres connect it outside
and in front with the fleshy tissue distributed round the spiracular cavity
•generally.
The interior of the narial chamber, except the sacs, is lined with dark pigmental
tissue, and in the more upright portion of the walls is thrown into narrowed wavy
corrugations which doubtless are effaced on dilatation of the chamber. I may
further call attention to a little glandular recess situated on the inner whorl of
the nasal cartilage and below the postnodular pad. Mesially there is a strip of
septal cartilage.
Fig. 15.
A vertical section through the head of Platanista gangetica, slightly to the right of the median line, designed to
show the spiracular cavity and sacs, the fibrous blubber of the forehead, interior of brain cavity, and nerves
supplying the teeth. The snout is curtailed, and the lower jaw, tongue, &c., have been cut away. Drawn
from nature and reduced about -|rd nat. size,
o, skin of the left side of the orifice of the blow-hole (an arrow is directed downwards through the spiracular
cavity, and its point is shown passing into (pn) the posterior nares); bl, the coarse fibrous tissue and blubber
and fibrous material o f the forehead, and whioh substance reaches quite to the top of the skull; ca, cartilaginous
piece in the blow-hole; p , pad, immediately to the inside of the latter \ a Sf b, fibrous elevations or
cushions in,front wall of spout-hole, and here seen in section; I, lowermost nasal sac (premaxillary) ; II,
orifice of lateral sao (maxillary), the dotted line signifies its position, otherwise it is hidden in the fleshy
Substance ; III, narrowed spiral canal which passes partly round (ca) the nasal cartilage and constitutes the
small third nasal sao ( = nasofacial); s, cartilaginous septum nares; pmx, premaxillary bone | mx, maxillary;
v, vomer; p , pterygoid; f , frontal; bs, basi-sphenoid; bo, basi-occipital; c, occipital condyle; so, supra-occi-
pital; 5, sphenoidal fissure; 7, internal auditory foramen; 8, fissure exit of eighth pair of nerves; g, condyloid
foramen; m, neck muscles; n, branches of superior dental nerve.
Posterior Nares.—(Woodcut, Eig. 15, p n ; also PI. XXVIII, fig. %,pn.)—The
internal nasal aperture is a longitudinally elongated.1 oval opening, 2 inches in
length, and one in breadth in the adult, and its margin is thick and fleshy. Its
posterior border is slightly behind the posterior margin of the basi-occipital bone.
I t dilates between its margin and the posterior end of the pterygoid into a sac which
fills up the downward and outwardly projecting plate of the basi-occipital and
basisphenoid, and runs forward to the pterygoids. The sac thus [fills up the triangular
surface on, the base of the skull, defined by these osseous parts, and in consequence
is of considerable capacity, triangular in form, with the apex directed forwards
to the osseous nasal septum; having a length of nearly 3 inches, and a breadth
of 1*50 inch. The walls of this portion of the nasal canal originate external to the
internal nares, so that they form a kind of imperfect floor to the sac, projecting
internal to its walls for nearly an inch and a half anteriorly, but only about half an
inch posteriorly. The front and sides of the opening are thick, while the posterior