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



Action. — This muscle is a powerful extensor of the head and neck. Its arrangement 

 is such as absolutely to prevent the entire elimination of the well-marked curve forwards 

 of the lower portion of the cervical vertebral column, without rupture of the fibres 

 which compose the muscle. 



Relations. — The muscle in the dorsal region is concealed by the trapezius and rhom- 

 boid, and lies in a groove formed by the subjacent vertebral muscles. In the neck it is 

 not in contact with the vertebral column, but forms a chord to the curve of the lower 

 cervical vertebrse. 



Nerve supiyly. — Numerous branches from the posterior divisions of the dorsal and 

 cervical spinal nerves. 



Remarks. — The description of this muscle just given applies to every species of 

 Penguin which I have examined. The attachment of the biventcr cervicis so low down 

 as the iliac crest, and the remarkable relation above referred to, which the muscle bears to 

 the lower cervical vertebrae, are doubtless related to the upright position which these birds 

 invariably assume when on land. 



2. Complexus. 



Complexus, Vicq d'Azyr, 1773, p. 581, No. 5. 



Der Kopfdreher, Mei'rem. 



Grand complexus, Cuvier, vol. i. p. 237. 



Dei- durchflochtene Mvslcel, Tiedemann, p. 284, No. .5. 



Complexus, Owen (Todd's C^'clopffdia, vol. i. p. 291). 



Muscle No. 2, Meckel, vol. vL p. 12. 



Complexus, Selenka, vol. vi. p. 98, No. 14. 



Grand complexus, Gervais and Alix, p. 15. 



Attachments. — The complexus arises by means of tlu-ee distinct slips from the tips of the 

 bony spines of the posterior articular processes (hyperapophyses of Mivart ^) of the third, 

 fourth, and fifth cervical vertebrae. The fibres pass forwards and are attached above the 

 insertion of the biventer cervicis to the upper end of the transverse crest of the occipital 

 bone. 



Action. — The muscles of opposite sides acting together extend the skull upon the 

 vertebral column. 



Relations. — The complexus is concealed by the cutaneous muscle of the neck, and 

 rests upon the splenius capitis. The tip of the hyoid cornu lies between the outer side 

 of this and the posterior border of the digastric muscle. 



Nerve supply. — A branch from the posterior division of the second cervical nerve. 



Variations. — In Spheniscus mendiculus the origin of the muscle is confined to the 

 fourth and fifth cervical vertebrae. 



' Trans. Zool. Soc, vul. viii., pt. 7, 1874. 



