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



Action. — This muscle extends tlie neck, and rotates the vertebrae upon one another, 

 so as to direct the head towards the side on which the muscle acts. 



Relations. — The splenius colli at its origin is in contact with its fellow of the opposite 

 side. Its outer side is in contact with the insertion of the extensor magnus colli. A few 

 of the fibres at its insertion are continuous with those of the rectus capitus lateralis. 



Nerve supply. — Branches from the posterior divisions of the cervical nerves. 



Variations. — In Spheniscus minor the origin of this muscle is limited to the arches of 

 the sixth, seventh, eighth, and ninth cervical vertebrae. In Spheniscus magellanicus it 

 arises from the fourth to the ninth cervical vertebrae inclusive. In Spheni.^cus demersus 

 the splenius colli arises from the second to the ninth cervical vertebrae inclusive, and is 

 inserted into the hyperapophyses of the second and third cervical vertebrae. In 

 Spheniscus mendiculus and Eudyptes chrysolophus it is likewise inserted into the second 

 and third cervical vertebrae. 



5. Extensor colli tertius. 



The muscle which I have thus named is present in nearly every species of Penguin, 

 and consists of a delicate slip which lies between and separates the splenius colli and the 

 extensor longus colli. It arises from the arches of the seventh and eiohth cervical 

 vertebrae, and passing oliliquely forwards and outwards, is inserted into the posterior 

 articular process of the fifth cervical vertebra. 



Action. — It extends the neck. 



Va7'iations. — This muscle is absent in Spheniscus mendicidus and in Aptenodytcs 

 longirostns. 



6. Extensor parvus colli. 



Der Meine Hulsstreclcer, Wiedemann, p. 77. 



Der kleine HaUstrecIcer, Tiedemann, p. 287, No. 3. 



Ohliqmis colli, Owen, p. 26. 



Attachments. — This muscle is divisible into two parts, an upper and lower. The loiver 

 portion arises by means of a number of separate slips from the transverse processes of the 

 five posterior cervical vertebrae. The fibres pass forwards, and are inserted into the 

 posterior articular processes of the fifth to the ninth cervical vertebrae inclusive. 



The iipper portion arises from the transverse processes of the sixth to the ninth 

 cervical vertebrae inclusive, by means of distinct muscular slips. These slips unite to 

 form a single muscular belly, which is inserted into the posterior articular process of the 

 third cervical vertebra. 



Action. — This muscle extends the neck, and directs it towards the side on which the 

 muscle acts. 



