230 THE VOYAGE. OF H.M.S. CHALLENGER. 



The Spinalis colli in Arctocephalus branches off from the spinalis dorsi between the 2nd and 

 3rd dorsal vertebrae, passes forwards, receives additional fibres from the posterior cervical spine, 

 surmounts them, and ends on the neural spine of the axis. It is inserted into the anterior cervical 

 spines as far forwards as the axis. 



The Complexus in Phoca vitulina lies above the rectus capitis posticus major, and beneath the 

 splenitis capitis and trachelo-mastoid. It is a fleshy band, and arises from the zygapophyses of the 

 3rd to the 7th cervical vertebrae by fleshy digitations. The fibres proceed to the occipital region, and 

 are inserted by tendon in its inner three-fourths and by muscular fibres in its outer fourth into 

 the back of the interparietal element of the occipital bone, and into the occipital ridge, reaching 

 nearly to the root of the zygoma. It is supplied by the internal branches of all the cervical, and 

 a branch of the suboccipital nerve. 



In Arctocephalus it arises from the hyperapophyses of the 3rd, 4th, 5th, 6th, and 7th cervical 

 vertebras, and the metapophysis of the 3rd cervical. It courses forwards upon the cervical laniinas, 

 and is inserted by tendon into the occipital ridge to the outer side of the biventer cervicis. 



The Biventer cervicis in Phoca vitulina arises by fibres from the anterior zygapophysis of the 

 7th cervical vertebra, from the posterior zygapophysis of the same, from the anterior and posterior 

 surfaces of the 1st dorsal vertebra, and from the anterior part of the 2nd dorsal vertebra. There 

 are three digitations of origin; at the spine of the axis it unites with the inner border of the 

 complexus and is inserted with it. In the large Phoca vitulina it arises from the zygapophyses of the 

 1st to the 4th dorsal vertebras, and joins the complexus opposite the spine of the axis. In a small 

 male Phoca vitulina it was absent. The nerve supply is the same as that of the complexus. 



In Arctocephalus it is long and riband-like. It arises from the roots and sides of the neural spines 

 of the 2nd, 3rd, and 4th dorsal vertebrae to the inner side of the trachelo-mastoid, with which it is 

 blended at its origin. It passes forwards to the inner edge of the complexus, and is inserted by 

 fibres into the occipital ridge, between the complexus on its outer side and the sagittal suture 

 on its inner. 



The Oblique Rotator Muscle of the Spincd Column} — This muscle is in two layers in Phoca vitulina 

 and in Arctocephalus, and lies between the neural spines and the zygapophyses. These layers are 

 of a totally different formation in these animals. In Phoca the superficial layer is an extensive 

 muscular bundle extending from the caudal to the cervical region, and the deeper layer forms a set 

 of triangular imbricated muscles. In Arctocephalus the superficial layer resembles the deeper layer 

 in Phoca, and the deep layer is similar of the rotatores muscles in human anatomy. 



The superficial layer of fibres of the oblicpue rotator in Phoca vitulina lies in the hollow 

 between the neural spines and the zygapophyses, stretching from the caudal region into the 

 cervical under cover of the lumbo-dorsal fascia. In the caudal region the origins are tendinous 

 slips ; the first slip arises from the rudimentary zygapophyses of the 4th and 5th caudal vertebras 

 and the dorsal surfaces of the laminas between them, and is inserted into the side of the neural 

 spine of the 4th sacral vertebra, the corresponding parts of the 1st, 2nd, and 3rd caudal, and also 

 into the posterior part of the zygapophyses of the 3rd caudal ; the second slip arises from the 

 zygapophysis of the 3rd caudal vertebra, and is inserted into the sides of the neural spines of the 

 2nd and 3rd sacral vertebra 3 , and the laminae between the 2nd and 3rd, and 3rd and 4th sacral 

 vertebras ; the third slip arises from the zygapophysis of the 2nd caudal vertebra, and is inserted 



1 See for the use of this term Sir Win. Turner's Introduction to Human Anatomy, revised edition, p. 76, 1882. 



