AMERICAN WHITE PELICAN. 
187 
nation of several individuals in stating, is destitute of the horny crest of the 
upper mandible. 
A male, shot near Grande Terre, in the Gulf of Mexico, examined* The 
skin is very thin, but the subcutaneous cellular tissue is extremely developed, 
forming a thick reticular layer over the whole body. The internal cells are 
also of vast size, the right hepatic being 4-J- inches long, the right abdominal 
4\ by 4 ; the left abdominal 54 by 4 ; the clavicular cell is not formed by a 
single cavity, but of numberless cellules, like those of the subcutaneous tissue. 
The heart n is triangular, pointed, 3 inches long, 2 inches and 10 twelfths in 
breadth ; the aorta branches at the base, as in other birds, sending off the 
two trunks which separate into the subclavian and carotid. The lobes of the 
liver are extremely unequal, the right, o, being 4 inches in length, and 2i 
in breadth, while the left, p, is only 2 inches long, and 1| inches broad. 
The mandibles are entirely covered with skin, of which the subcutaneous 
tissue is wanting, the cutis condensed, and the cuticle in large irregular 
longitudinal plates, leaving the surface somewhat rough and scaly. The 
crest-like excrescence on the ridge of the upper mandible is not formed of 
bone, nor otherwise connected with the osseous surface, which is smooth 
and continuous beneath it, than by being placed upon it, like any other part 
of the skin, and when softened by immersion in a liquid may be bent a little 
to either side. It is composed internally of erect slender plates of a fibrous 
texture, externally of horny fibres, which are erect on the sides, and longi- 
tudinal on the broadened ridge ; these fibres being continuous with the cutis 
and cuticle. The skin of the mandible is continuous with that of the pouch, 
of which the structure is as follows : Externally there is a layer of cuticle, 
beneath which is the cutis, extremely thin, and with the cuticle thrown into 
longitudinal rugae when contracted. The internal surface is also of cuticle, 
and beneath it is a layer of cutis. Between these two very thin layers of 
skin, is interposed an equally thin layer, composed of two sets of very 
slender muscular fibres, separated from each other, and running in two oppo- 
site directions. The outer fibres run in fasciculi from the lower and inner 
edge of the mandible ; those from its base pass downwards, those arising more 
anteriorly pass gradually more forwards, and spreading out, reach the middle 
line of the pouch. The inner fibres have the same origin, and pass in a con- 
trary direction, backwards and inwards. From the hyoid bone to the junc- 
tion of the two crura of the mandible, which takes place almost at the very 
tip, there extends a thin band of longitudinal muscular fibres, in the centre 
of which is a cord of elastic tissue. By means of this apparatus, the sac is 
contracted, so as to occupy little space. When the bill is opened, the crura 
of the lower mandible separate from each other to a considerable extent, by 
the action of the muscles inserted into their base, this depending upon their 
