146 DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 
it is inserted mesially from the third chevron bone, backwards to the termination of the 
spinal column, and outwardly is fixed to the tips of the transverse processes. Anteriorly 
the muscle is strong, thick, and very fleshy; but halfway along the tail, and nearly 
throughout the middle line, it becomes tendinous, by degrees thinner, and towards the 
end is little else than a dense glistening aponeurotic fascia with coarse tough fibres. 
These fibres, when unravelled with care, separate into broadish tendons, one to each 
vertebra, which posteriorly commingle with the great flat tail-aponeurosis. 
The second or deeper muscular lamella, also taper-shaped, is as a whole much 
thicker and fleshy, but not quite so broad as the last. Besides a very small slip ante- 
riorly derived from the last rib, it has firm attachments along the under surfaces of the 
two lumbar and all the caudal vertebre, filling the interspace betwixt the vertebral 
bodies, the sides of the chevron bones, and the distal extremities of the transverse 
osseous elements. This sheet, like the former superficial one, is fleshy anteriorly and 
tendinous inwardly and behind. Its terminal fascize or tendons are more cord-like, and 
with less difficulty resolvable into separate elements. The direction of the fibres of 
no. 2 are somewhat more backwardly oblique than no. 1. 
Neither of these two muscles, be it noted, passes underneath the diaphragm, but 
stops short quite abreast of its posterior surface. 
The next muscle (or pair of muscles) is very diminutive compared with the foregoing. 
It lies on the inner and anterior aspect of the deep caudal layer, and partly passes for- 
wards beneath the diaphragm. ‘The innermost and slightly longer of the two arises by 
tendinous and fleshy fibres from the sides of the bodies of the last two dorsal vertebrae 
and of the vertebral end of the final rib; narrowing posteriorly it is inserted on the first 
chevron bone. The outermost is attached in front to the last rib and behind to the 
outside of the same chevron bone as its neighbour. Nerves apparently representative 
of the lumbar plexus issue between these two muscles. 
Lastly, if considered amongst the subcaudal muscles, and not what it to some extent 
simulates, a continuation of the sacro-lumbalis, we have the lateral or superficial out- 
lying fusiform muscle intermediate between the dorsal and ventral surfaces of the tail. 
This numerically fifth infracaudal muscle, narrow, roundish, and tapering, has origin 
close to the termination of the sacro-lumbalis, from the cartilaginous tip of the trans- 
verse process of the sacral or first true caudal vertebra, and lies horizontally along the 
next eight processes. It terminates in a long but strong tendon upon the surface of the 
subcaudal muscle (Sc), mingling with its fascia. 
My interpretation of these muscles is, that the superficial great broad layer represents 
an expanded sacro-coccygeus, in this case extending more than usually forwards, and 
the caudal tendons (each separate in most quadrupeds) are here coalesced into an apo- 
neurotic sheet, adapted to the osseous and anomalous fleshy tail-formation. The layer 
beneath is an enormously developed infracoccygeus, with which muscle it corresponds 
in position &c. The anterior pair of small slips agree best with the guadratus lum- 
