164 DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE, 
23 inches broad and 13 inch thick at this point); thence it passes forwards and out- 
wards (P.c’) on the neck, beneath the platysmal cross fibres, ultimately being inserted 
as a broad and strong tendinous sheet into the malar bone, posteriorly and inferiorly to 
the first portion of the panniculus, as already detailed. 
Superficial to the shoulder and sternal segments, and as it were forming a bridge 
between them in front of the pectoral extremity (P.c’), is what appears as a platysma 
myoides. ‘This is represented by a coarse thin sheet of muscle interspersed with much 
fatty tissue. The fibres may be said to arise from the inferior median surface of the 
neck and mandible for several inches in breadth, intermingling there with those deeper 
segments of the panniculus mentioned above. Crossing the neck in a transverse direc- 
tion, the fibres radiate slightly, and are firmly but superficially intertwined with those 
of the lower border of the outer nuchal panniculus, whilst fibrous tissue and fat connect 
them with the infraspinatus. A narrow slip of the muscle extends downwards on the 
anterior border of the limb as low as the middle of the biceps, whence, becoming 
fibrous, it descends as a cord-like body as far as the base of the metacarpal bone of the 
first digit (P.c’*, fig. 13). 
At the anal or posterior end the fibres of the panniculus diverge triradially (P.c***), 
a broad portion curving gently outwards; and the intermediate portion (larger) ends 
wedge-shaped with inwardly inclined fibres, which, along with its fellow of the opposite 
side, are inserted by strong aponeurosis between the depressores caudée into the sixth 
chevron bone. 
In the female there was also observed another fleshy slip, about an inch broad, which 
was given off from the body of the muscle opposite the generative outlet; and this 
proceeded downwards and backwards, being likewise inserted into the skin on the 
median perineal region. 
Connected with the action of this subdermal muscle it may be remarked that, as in 
Cetacea, it can have little or no power over the skin itself, not being fastened thereon, 
a thick coating of fat intervening. On the other hand the attachments of the muscle 
point to its subserving the bodily force of various parts. For instance, the fixed points 
to the malar bones must give the advanced segment of the muscle a very long leverage 
for movements of the head; at the same time the insertion on the facial bones and lips 
must lend power to the labial muscles, and in some ways act as a dilatator oris, and 
impart additional strength to the thick muscles of the great muzzle. 
V. Tue Digestive Tract. 
1. Interior of the Mouth, and Tongue. 
The very curious structure of both the exterior and interior parts of the mouth has 
been a favourite topic of those who have contributed memoirs on M/anatus. Stannius’s 
account is, on the whole, the most explicit, though brief. In treating of the mandu- 
