DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 145 
exoccipital bone, betwixt the cephalo-humeral and the complexus muscles; the united 
superior obliquus and the rectus lateralis are situated below and within. 
The splenius and compleaus appear almost a continuation of the long internal spinal 
muscle; there is, however, a distinct separation, excepting a few of the fibres. Of 
the two the splenius (Sp, fig. 8) is much the smaller. It diverges, so to speak, from 
the fleshy fibres of the complexus outwardly, opposite the second rib, and proceeds 
broadly to the skull, where it is inserted by a short, flat, but very strong tendon into 
the exoccipital ridge above and behind the cephalo-humeral. The larger, thick and 
long complexus arises from the outer side of the spinalis dorsi, above the head of the 
sixth nb. It covers the remaining interspace between the ribs and the compressed 
anterior portion of the spinalis dorsi forwards to the cervical vertebrae, where it spreads 
out and lies superficial to the short recti and oblique muscles. It is inserted into the 
whole of the back of the cranium, as far outwards as the paramastoid. 
The short deep muscles of the back of the neck are well represented, in spite of the 
diminution of the posterior cervical vertebre; for the atlas and axis are still of fair 
dimensions. ‘They show no deviation in attachments from those of crdinary mammals. 
The rectus capitis posticus major and minor have coalesced fleshy fibres, the former being 
much the larger of the two. The odliquus inferior is well developed, and somewhat 
fusiform. The obliquus superior and rectus lateralis are closely united, and together 
form a short fleshy band. 
These posterior short muscles of the neck Stannius’ partly treats along with the 
semispinales in the Porpoise; but in the Pilot Whale, Macalister? and myself have both 
found a very large rectus posticus, apparently major and minor. I have also defined 
obliqui in the same animal. In the Elephant* there are a distinct voluminous rectus 
capitis major, an obliquus superior, and obliquus inferior obtain. 
Ventral Aspect.—Before drawing attention to the descriptions and opinions of Rapp 
and Stannius concerning the presence and homologies of the infralumbar and subcaudal 
muscles of the Dolphin and Manatee, I deem it preferable to render an account of my 
own dissection of the parts in question. In Manatus five, or at least four, distinct 
muscular masses can be traced without difficulty, as superimposed in two broad flattish 
layers, with an additional lateral or outlying fusiform one. 
The first and notable muscle is that which in the profile and under-view appears as a 
great and the only mass filling the interval between the last rib and the caudal extre- 
mity, and the space between the chevron bones and the tips of the lumbo-caudal 
transverse processes. ‘This aspect is in some respects deceptive, as the muscle, when 
manipulated by the scalpel, is found to be only one of two thick and long layers 
occupying the area in question. The superficial stratum or musculo-tendinous lamella 
arises from the outer half and inferior surface of the last rib, being here partially 
overlain by the external oblique and panniculus; thence, with inwardly oblique fibres, 
? Loc. cit. p. 30. 2 Pp. Z.8. 1867, p. 481. * Myologie, pl. 282, lettered M’, N, and N*. 
Z2 
