144 DE. J. MUEIE ON THE FOEM AjST) STEUCTUEE OF THE MANATEE. 



Manatee. Here we find that definition into separate or individual muscles is not easy, 

 from the very fused condition of the parts. There may be traced, however, through the 

 length of the dorsal and what constitutes the lumbar region oblique sets of fibres 

 which answer to those of the multijidus spina; and semispinales. 



The lemtores costarum, corresponding to the number of ribs less one, are more easily 

 defined than the preceding ; but they also have their fibres much intermingled with the 

 long spinal muscles presently to be spoken of. 



As regards the interspnales, these either are aborted or so masked by the volume of 

 interspinal yellow elastic ligamentum subflavum that their function is supplanted by 



the latter. 



From that close adherence of the mass of the erector spinse to the tissues beneath, 

 intertransversales muscular slips are chiefly apparent in the lumbar and caudal regions, 

 reference to which shall be made further on. 



What corresponds to the combined or continuous spinalis dorsi and levator caudw 

 internus is a long, narrow, but, in the back, vertically deep muscle, which runs from 

 the neck backwards as far as the end of the tail. Anteriorly, where laterally com- 

 pressed but fleshy, it fills vertically the hollow between the cervical spines and trans- 

 verse processes. Posteriorly it becomes tendinous and aponeurotic, and is fastened to 

 the caudal vertebrae superiorly. 



There is a very massive and in great part fleshy longissimus dorsi, which extends 

 outside the last from the first rib backwards to the very end of the caudal vertebrae, 

 thus including what constitutes the levator caudw externus of most other Mammals. 

 Like the preceding the tail-tendons are interwoven into an aponeurosis, partially fixed 

 to the transverse and to the spinous processes. 



The well-marked sacro-lumbalis is a rather narrow but thick muscular elongation, 

 lying upon and firmly attached to the whole of the ribs outside their angles. Its outer 

 tendons are short and fixed to the costae along with the fleshy part of the external 

 border of the muscle ; the internal tendons are even more imbedded among the mus- 

 cular substance. At the first rib the sacro-lumbalis is very narrow, but is broader 

 towards the middle of the body — in the larger specimen being 2 inches in transverse 

 diameter. At the last rib there is a fusiform muscle, almost like a continuation of the 

 sacro-lumbalis, but which I shall describe along with the subcaudal series. A few 

 fleshy fibres are continued forwards on to the axis, from the sacro-lumbalis, and a still 

 larger amount from the longissimus dorsi ; but, as might be expected from the remark- 

 able shortness of the Manatee's neck, neither of these compressed bundles is of much 

 import functionally. They are indi^'idually homologues of the cervicalis ascendens and 

 transversalis colli. 



There is, moreover, a better representative of the trachelo-mastoid, which is a much 

 longer and distinct muscular band, proceeding forwards from the edge of the trans- 

 versalis colli, and is inserted into the skull. The cranial attachment is upon the 



