146 DR. J. MUEIE ON THE FOEM AND STRUCTUEE OF THE MANATEE. 



it is inserted mesially from the third che\Ton bone, backwai'ds to the termination of the 

 spinal cohimn, 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 vertebrae, 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 fasciae or tendons are more cord-like, and 

 with less difficulty resolvable into separate elements. The direction of the flbres 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 Avhich muscle it corresponds 

 in position &c. The anterior pair of small slips agree best with the quadratus lum- 



