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



vertebra. It is inserted into the back of the hatchet-shaped neural spine of the axis, into the 

 posterior border of its lamina, and into the neural spine of the 3rd cervical vertebra. The second 

 arises from the hyperapophyses of the 5th, 6th, and 7th cervical, ascends, and is inserted into the 

 neural spines of the 4th and 5th cervical. The third arises from the hyperapophysis of the 7th 

 cervical and the posterior zygapophysis of the 1st dorsal vertebra, and is inserted into the back 

 of the neural spine of the 5th and the neural spine of the 6th cervical. The dorsal muscles 

 are well marked in the anterior dorsal region, but are feeble near the lumbar, for the space between 

 the transverse processes and the neural spines narrows considerably near the lumbar region. They 

 are all formed on the same plan, and arise from the inner sides of the transverse processes of these 

 vertebrae, and are inserted into the side of the neural spine opposite the most anterior vertebra 

 from which they spring. 



The deep layer of the oblique rotators in Arctocephalus arises from the anterior of the transverse 

 processes, passes inwards, and is inserted into the roots of the neural spines and posterior borders 

 of the lamina? of the vertebra? anterior to their origin. 



The erector spinas, sacro-lumbalis, longissimus dorsi, transversalis colli, trachelo-mastoid, and 

 spinalis dorsi are supplied by the external branches of the posterior divisions of the cervical, dorsal, 

 and lumbar nerves. The rotator muscles and spinalis colli by the internal branches of the posterior 

 divisions of the cervical, dorsal, and lumbar nerves. 



The Supraspinales were not seen in Phoca vitulina or Arctocephalus. 



The Intcrspinales in Phoca vitulina and in Arctocephalus are most distinct in the cervical 

 region. 



The Intcrtransvcrsalcs in Phoca vitulina and in Arctocephalus are found in the cervical and 

 dorsal regions. In the latter they are between the dorsal divisions of the transverse processes. 



The Intcrzygapophyscs in Phoca vitulina and in Arctocephalus, in the lumbar region, are strong 

 muscular slips. The supraspinales and interspinales are supplied by the internal divisions of the 

 cervical, dorsal, and lumbar nerves. The intertransversales and interzygapophyses by the external 

 divisions of the cervical, dorsal, and lumbar nerves. 



The Rectus capitis posticus major in Phoca vitulina is riband-shaped and arises from the posterior 

 three-fourths of the side of the tip of the neural spine of the axis by muscular fibres. It courses 

 forward, and is inserted by a short tendon into the lambdoidal suture between the rectus capitis 

 posticus minor and the rectus capitis posticus major accessorius behind the occipital ridge beneath 

 the complexus. It is supplied by the suboccipital nerve. 



In Arctocephalus it arises from the anterior two-thirds of the side of the hatchet-shaped neural 

 spine of the axis, and slightly from the adjoining surface. It is inserted into the lambdoidal suture. 



The Rectus capitis p>osticus major accessorius is present in all the specimens. It is a narrow mus- 

 cular slip arising by muscular fibres from the anterior fourth of the side of the tip of the neural 

 spine of the axis. This small bundle takes a turn outwards and ascends to the occiput between the 

 rectus capitis posticus major and minor. It is inserted into the occipital bone a little posterior to 

 the lambdoidal suture, to the inner edge of the rectus capitis posticus major, between the insertion 

 of the rectus capitis posticus minor and the insertion of the superior oblique, and slightly into 

 the back of the condyle of the occipital bone, posterior to the major. It is supplied by the 

 suboccipital nerve. 



In Arctocephalus it arises from the anterior and under surface of the neural spine of the axis, and 



