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



which passes forwards, and ends opposite the 8th dorsal vertebra, and covers the whole of the 

 longissimus division in the lumbar region, and 1 inch of the sacro-lumbalis division next the 

 ilium ; also from the neural spines and zygapophyses of the caudal vertebra;, from the neural 

 spines, zygapophyses, and transverse processes of all the sacral vertebra?, from the inner surface of 

 the ilium, from the anterior surface of the sacrum, from the ligament between the ilium and sacrum, 

 from all the lumbar vertebra? between the neural spines and the zygapophyses, and from the sides 

 of these vertebras between the zygapophyses and the ventral tips of the transverse processes. 



The Eio-costcdis or Sacro-lumbalis in Phoca vitulina is the outer division of the erector spina?. 

 It is a long band running along the back, broadest and strongest at the posterior end, narrowest 

 and tendinous at the anterior. Along its outer margin is a series of serrations, the seven posterior being 

 muscular, the nine anterior tendinous. It is chiefly adherent to the outer surfaces of the ribs over 

 which it lies, especially along their posterior and anterior borders. It is inserted by the digitations 

 along its outer edge into the outer surfaces of the posterior seven ribs by muscular fibres, into the 

 posterior borders of the anterior seven ribs by tendinous slips, and into the dorsal tubercle of the 

 transverse process of the 7th cervical vertebra. In the large Phoca vitulina it also arises by 

 tendinous slips from the angles of the 14th to the 5th ribs on their anterior borders. It is supplied 

 by the posterior primary division of the spinal nerves. 



In Arctocejthahis it is an offshoot from the erector spina?, and its origin can be partly traced 

 to 1 inch anterior to the crest of the ilium. It is very narrow posteriorly, and expands gradually 

 as it approaches the last rib, where it covers its inner two-thirds, while the anterior two-thirds of 

 the muscle is narrow and tendinous on the dorsal surface, and terminates by giving off long tendinous 

 slips. It is inserted into the dorsal surfaces of the 6 th to the 15th ribs. Along its outer margin 

 it has a number of tendinous digitations which are long at the anterior end, and short posteriorly. 

 The most anterior goes into the dorsal tip of the transverse process of the 7th cervical, the rest 

 pass to the dorsal borders of the 1st to the 12th ribs. The posterior slips are half tendinous and 

 half muscular. 



The Musculus acccssorius ad ilio-costalcm and the Ccrviccdis ascendens are wanting in both Phoca 

 vitulina and Ar otocephalus. 



The Longissinms dorsi in Phoca vihdina lies to the inner side of the sacro-lumbalis, but is not 

 quite so large or long, and is under cover of the fascia lunibo-dorsalis. It arises from the under 

 surface of this fascia out of the erector spina?, from the dorsal tips of the zygapophyses of some 

 of the lumbar vertebra?, and from the anterior zygapophyses of all the dorsal vertebra?. It lies 

 along the outer side of the zygapophyses, and is inserted by muscular fibres into the outer surfaces 

 of the posterior five ribs, by tendons into the anapophyses of some of the dorsal vertebra? (posterior 

 six), into the dorsal tips of the transverse processes of all the other dorsal vertebra?, which are 

 homologous to the anapophyses, into the dorsal division of the transverse process of the 7th cervical 

 vertebra, and by tendinous slips along its inner border into the dorsal surfaces of the anterior 

 borders of the 6th to the 11th ribs. From the anterior zygapophyses of the 11th and 12th dorsal 

 vertebra? two strong tendons arise, which divide equally between the multifidus and this muscle. 

 Opposite the 6th rib a large piece of this muscle goes into the transversalis cervicis. In the large 

 Phoca vitulina it is inserted in addition into the 9th. 10th, and 11th ribs on their posterior surfaces. 



In Arctoccphalus it is a long narrow band covered by dense fascia in its posterior half. This 

 division of the erector runs into the neck, giving off a number of serrations from its under surface, the 



